looking for pros and cons. thanks

 

Between those two, all of the pro's go to the LB9 heads and all the cons to the 624's.

Unless you're looking for door stops.

 

the doner engine im installing for now is a 84 cfi 350. the heads are 76cc. will my 58cc lb9's at too much compression? the engine is a 14010207.

 

The block casting #, while somewhat informative, doesn't say anything about the pistons that are installed, which are what is critical in determining CR.

No matter how you slice it, 624 heads are horrible. Until they are gone, there isn't much you can expect performance-wise.

The 416 heads can be worked to increase the chamber size if necessary. 1.94" intake valves, basic port clean-up, and valve de-shrouding will probably get you there. And that's just assuming the pistons are flat tops with 4-valve reliefs, which probably isn't the case. And, they'll out-perform 624's, even if the 624's have 2.02/1.60 valves.

 

are 416's stock lb9 heads?

 

For '85 & '86, yes. '87-up had 081's.