OK, I will give a try. Feel free to add or modify to these as necessary:
Front axles:
Stock Land Cruiser Axles Front Axles:
1. strength: in stock form can handle moderate wheeling up to a 33" tire with little breakage.
2. weight and clearance: Lighter axle with good clearance
3. aftermarket Upgrades: Newer Birfs (longs, newfields, smurfs) will add strength and can handle moderate to heavy wheeling up to a 38" tire with little breakage. Add in over 38" tires and a V8 possibility of destruction goes up.
4. what will be the weak link: In stock form the Birf, or lockout. With aftermarket Birf it will be the inner axle or lockout(except asins).
Pros: Available and cheap, good clearance and aftermarket support.
Cons: Inner axles are getting harder to find. Stock coarse spline Pinion is weak. Need some Upgrades to handle above a 33" tire with little breakage.
Dana 44 Front Axles:
1. strength: in stock form can handle moderate wheeling up to a 33" tire with little breakage.
2. weight and clearance: Lighter axle with good clearance
3. aftermarket Upgrades: CTM ujoints will add strength and can handle moderate to heavy wheeling up to a 38" tire with little breakage, but need custom inner high-grade steel axles to be effective. Add in over 38" tires and a V8 possibility of destruction goes up.
4. what will be the weak link: In stock form the ujoint, axleshafts, and balljoints. With aftermarket Ujoints and axles it will be the lockout or possibly the pinion.
Pros: Available and cheap, fairly good clearance and great aftermarket support.
Cons: Has Ball Joint axles which break too easily. Need some Upgrades to handle above a 33" tire with little breakage.
Dana 60 Front Axles:
1. strength: in stock form can handle moderate wheeling up to a 38" tire with little breakage.
2. weight and clearance: heavier axle with less clearance
3. aftermarket Upgrades: CTM ujoints will add strength and can handle moderate to heavy wheeling up to a 42-44" tire with little breakage, but need custom inner high-grade steel axles to be effective and need D70(35spline outers). Add in over 44" tires and a Big Block V8 possibility of destruction goes up.
4. what will be the weak link: In stock form the outer stub shaft(30spline). With aftermarket Ujoints and axles it will be nearly indestructible, probably differential would be the weak link or other drivetrain parts.
Pros: Great aftermarket support, and can be built Very Strong
Cons: Expensive
Volvo C303 Front Axles:
1. strength: in stock form can handle moderate wheeling up to a 38" tire with little breakage.
2. weight and clearance: heavier axle with a lot clearance (portal)
3. aftermarket Upgrades: High strength birf available and custom machined detroit will increase strength. No portal box upgrades that I know of that would handle over a 42 effectively without stripping portal gear. Though some suppliers are working on.
4. what will be the weak link: In stock form the factory locker spline. With aftermarket birfs and custom Detroit it will be the portal reduction gear.
Pros: Great Clearance due to the portals, and lighter than other portal axles.
Cons: Expensive, Very Hard to locate (Importing) and little aftermarket support. Moderate vehicle modification to fit properly.
Measurements:
WMS to WMS: ~70"
Axles Splines: Inner 27 spline
Ring Gear Dia: 8"
Pinion Offset: 6.25" from center to pass side
Tube Dia: 3.25" square tube
Portal Drop: 4.5"
Unimog 404 Front Axles:
1. strength: in stock form can handle moderate wheeling up to a 44" tire with little breakage.
2. weight and clearance: heavy axle with the most clearance (portal)
3. aftermarket Upgrades: High strength inner axles available will increase strength of smaller diameter short side inner axle. No portal box upgrades that I know of that would handle over a 44" effectively without busting portal gear reduction box. Look to 406/416 axles for slightly more beefy portal boxes, or U1300 axles for tires over 46".
4. weaklink: In all forms of 404 axle the portal reduction box will be the weak link.
Pros: Awesome Clearance due to the portals, and great turning radius, high pinion
Cons: Expensive, harder to locate than some axles, no aftermarket upgrade for the portal box. Heavy vehicle and axle modification to fit properly.
Measurements:
WMS to WMS: 69" Front, 68" Rear
Axles Splines: Inner 8 spline
Ring Gear Dia: 9"
Pinion Offset: 3.75" from center to drivers side in front, pass side in rear
Tube Dia: Tapered Double wall tube
Portal Drop: 4 3/8th"
Rockwell 2.5 Ton Front Axles (ujoint style):
1. strength: in stock form can handle moderate wheeling up to a 44" tire with little breakage.
2. weight and clearance: massively heavy axle with less clearance.
3. aftermarket Upgrades: High strength inner axles available require custom spiders or Detroit will allow for tire up to 53" or more.
4. what will be the weak link: In stock form the factory 16 spline axle shafts. With aftermarket axles and detroit these will be nearly indestructible even with 53s and a Big Block, I would guess the pinion would go or the rest of the drivetrain.
Pros: Cheap, high pinions
Cons: Very Heavy and tall axle (top loader). Moderate vehicle modification to fit properly.
These are just a few. If I get a chance and some research I may add measurements on clearance, gears available, and other stuff. Just need more time.
OH and question 5. I run Unimog 404 axles, narrowed with pinion conversions, disc brakes and custom inner axles. I like what I have, but would like to improve them slightly to lessen the weight on the next vehicle I build.