Yes the 305 uses 1.85" intake valves ,which if used will give you greater port velosity that you will feel over running the 1.94" valve,especially in the lower RPMs which most typical driving is in the lower RPM range.
Also,the 1.85" valves will be better on fuel over the 1.94" valves,if that's a concern.
I am pretty sure if you cc'd your cylinder head,measure how far down your pistons in the hole. Add up all those CC's.
Poor deck height,most likely.
Your engine probably has 8.2- 8.5:1 tops, that is why I suggest running the 194 clyinder head as to bring up your compression ratio closer to 9.2-9.5:1
Running a 1.85" intake valve in the 194 cly head does not require much chamber unshrouding, & really not too necessary for your application.
I would throw in some 1.60" exhaust valves also.
Hope this helps.
MBHD
