I'm trying to desktop my old motor but having a bit of trouble it's a 502 crane #139631 cam,GM rect. pocket ported heads, off the motor cc at 112.5, gil dry pipes. I don't think anything was done with the block so deck height should be stock, and has stock 502 mag. pistons JE700. Holley 800 dbl. pump. Dart single plane int. Desktop only has a few head choices I tried a few combos with GM 990 flow rates, also exhaust wasn't sure which to use I thought small tube open header. Finding comp. ratio I didn't know #'s for raised piston with valve reliefs. If any boaters can help I'd appreciate it...Thanks

Use the "advertised spec" on the cam, not the .050" values (I've never seen good figures from the .050 numbers).

990 should be fine.
small open headers will be close enough.
(oww, I think I just destroyed my knee hauling my lard utt off the couch to answer the phone that was 4 feet away from me..)
anyhow - use 8.75:1 with the 112.5cc heads.

It's a cool tool, but you got to get some seat time with it to really nail it down (Im no expert on it).

Thanks MC i'll give it a whirl