Just confirming, picking up a car with a rebuilt 327 that started with a 350 block...assuming he used a large journal 327 crank and 327 pistons, correct? Any special machine work needed here or a drop in? Just want to pick the guys brain so I can be sure if its a 327 or a 350. Can I tell the crank ID by the flange where the flexplate bolts up? Car is getting parted so the engine will be out for easy ID...actually thinking about it there could be a 307 crank in there too, right?

Correct, all thats needed to make a 327 outa a 350 is a LJ 3.25" crank and matching pistons.

I believe the "large journal" 327 and 307 cranks are the same casting number (cast) 3.25" stroke. The "large journal" "forged" 3.25" cranks are 327 only, found in the 4 bolt blocks ie 375/327. I don't know of any external 'tells' to id.

4672 327 Steel Large Journal 3.25
3911001 307-327 Cast Large Journal 3.25
3911011 307-327 Cast Large Journal 3.25
3914672 327 Steel Large Journal 3.25
3941174 307-327 Cast Large Journal 3.25
3951130 327 Steel Large Journal 3.25