ya know. as long as the crank isn't scored, you can simply change the bearings and leave the upper half alone. With that said, change your oil, folks - all of the scoring comes from that. The scoring reduces the oil pressure and causes the wear to the copper on the mains. 350 Chevy motors are so cheap. Steve (sgould) bought a 350 with low miles for $500 complete, TBI to accessories to pan - he is rebuilding it, but (and he agrees) could have run the motor as-is for a long time.
LS is an interesting idea, but it costs a lot more then most think.... here's a comparison I did on the 76 Corvette I'm building.
To update the decision-making process. Cost:
I have an LS motor, which would be great for this car - it's a 6.0 from a Denali. As with all things, it cost so I'll put that cost as part of this.
LS motor
1) Motor cost 2k
2) mounts, oil pan, bracket for only alternator 1,200
3) Cam $400
4) re-ring (it does have 190k on it), $500, bolts $200
5) headers - no one makes side pipes, yet, but I'd adapt OBX pipes so $800
6) adapters for LS motor exhaust, $100
7) flywheel $300 (for LS to ST-10 trans)
8) intake (either EFI or Carb the end number is about the same) $1200
9) misc $500
net hp 450
$7200
BBC 427
1) motor cost 1200
2) mounts, oil pan, alternator bracket. All interchanges except the alternator bracket $100
3) heads, rings, bearings, bolts $1500
4) cam $800
5) OBX stainless sidepipes $800
6) adapters zero
7) flywheel, zero, same as SBC that came out but to be fair 150
8) intake, carb, distributor (200, 400, 200) $800
9) misc $500
Net hp 700
$5850
SBC
1) motor cost $10,500 - for a 427 ci SBC
yeah... not going further
The strength of the motors is kind of a thing as well. By my own experience, at this hp level, the LS and the BBC are equal, even weight is within 50 lbs of each other.
Build the motor you need - that's kind of my point of reciting this. If you need north of 750 hp, you'd be a money-spending fool to do anything but LS (and I am one of those fools because of a Buick motor that's up soon to be assembled - no condemnation, just facts). I like the hp of a big-bore, short stroke motor (it's what I think Ford got right with the 302 - too bad the motor has a zip-strip up the cam bore). That said, you would not want to drive this in traffic, I think it's hp at idle is less then 100 hp (not kidding), it doesn't make 200 hp until almost 3000 rpm.... of course, at 3500 it makes 300 hp and at 6500 it makes 700 hp. But it will be a pain to drive (and that's fine, I know what I want and I frankly love it)... also, in its defense it makes nearly 400 lb torque at 2000 but be sure, it'll be a dog at anything less then 3000 rpm.
.
