Ok well here goes nothing, long story short I bought a 91 LS from a guy that said the car was a no crank, no start, well I bought the car and got it home and put a fresh battery in it, he was right, no crank, no start, I pushed it in the garage and pulled the plugs only to find out that #4 tip was gone, I pulled the head and he shattered the piston into a million pieces and not only bent but broke the rod in half, bent an exhaust valve and broke 2 valve guides, well I got the motor apart and it had a hole clean through the block into where the A/C pump was at, luckily there was no contact with the A/C pump. Well I bought a block from Josh (radioactive77) and decided to mic the crank before I ordered parts to assemble the new block, well #4 journal is out of round @ 1.706 on one side and 1.74 90* from the initial measurement, every thing else checks out @ 1.7707-1.7717 with a consistent reading of 1.7707 on 1-3 rod journal, the mains read 2.1644 and #3 where my thrust bearings go has a reading of 2.1644 which again is within spec (2.1642-2.1651). My question is which crankshaft can I swap into my new block, I believe I can swap a b18a/b, b20b/z but I want to make sure that if that the case the stroke won’t be incorrect. Admin if this is in the wrong section please place accordingly. TYIA.
b18a/b and b20b/z all have 89mm stroke.
i know it’s kinda late now, but why not just throw in a b20z? or high comp b20b? it’s drop in and a great upgrade 
honestly, considering the carnage, i wouldn’t be reusing any of that engine. just my opinion though
I wish I could come across a B20 swap for $3-400 around my area, I’ve been looking for a wrecked 99-01 CR-V and have had no dice finding one
if you’re going to rebuild the ls, look into some pr3 pistons
edit: sorry. i meant p30
tiger japanese has the low comp b20 for $400 iirc, and the high comp for 550-6. not too bad. also, check car-part.com. its a junkyard search engine, you can see what is available in your area.