Why are you planning on going to a much SMALLER and WEAKER rear axle? I understand your drive line angles but a DC drive shaft will solve the vibration issues.
However, if you are stuck on running smaller, weaker junk... A 4.11 (4.10 not available) 8.8 with rear disk (has built in parking brake, not sure if u were wanting that or not) will only be found in a Ford Explorer Sport Trac. The exploder pickup thingy if you are not familiar. If it were me I would have a DC rear shaft made, or get a 14B FF (semi float and full float models were made) and if you are set on 6 lug machine the hubs and axles down and re-drill the hub for 6 lug. Any competent machine shop can do this for you with no issue. A friend was gonna do just that but then decided to just go to tons front and rear and run em full width on 8 lug wheels.
But I really gotta ask. Why did you decide to run the D300? I'm not saying it is a bad t-case, but it seems you could of had other options for similar price that would still have passenger drop rear output solving the whole axle issue.
Oh and with 33's and the auto 4.10 / 4.11 will be a pretty good number, ideally 4.56 would be a similar to stock and would give you much more grunt offroad, but I think you would be ok with the 4.10 / 4.11, even more since it seems you are focusing of street performance.
Not sure if you intended for your post to read as it does, but I feel like I have to defend my post. So, first of all, I don't see how you can say the 8.8" axle is junk . . .
Second of all, I think you're misinformed about the 8.8's configuration. 4.10 is indeed the ratio that was available, and they disc brake equipped axles which I intend to run, have DIH parking brakes. . .
Finally, I have my mind set on the 8.8 / D300 for a few reasons:
1. I've done the math, the FJ60 rear & D300 combo = nasty compound angles. I'm not building an off-road buggy (been there done that), I intend for this truck to be a smooth running daily driver that sees camping duty & light offroad action. As such, I'm not willing to accept vibs. To eliminate, I would need to run a DC joint at both ends of the shaft & that's not even a guarantee.
2. The 8.8's are available with factory disc, close to the factory track width, and don't scrape the pavement with a low slung diff - can't say that for a 14 bolt.
3. My 60 axle has nasty pinion slop & is in need of a full rebuild, for the cost I'll have into parts, I can swap in a "new" low mileage axle.
4. The D300 bolts right up to my A341E after I swap the output w/an AW4 & it's a stout, compact t-case.
5. The D300 is clockable & I will be able to run a flat x-member.
6. I picked up this D300 for like $75 bucks
Only real drawback to the 8.8 is the 5 lug pattern. I will run aftermarket shafts (not enough space to re-drill) & will re-drill the rotors - no need for a machine shop when I have the equipment in my shop.
