Several questions about engine in '68, looking for facts and opinions please.

[Moneypit]

I took the heads of the engine in my 68 which I was led to believe to be the original 307. The machine shop called me and told me the heads were for a 305 so this brought up a few questions.

1. Will any of the numbers on the block be able to tell me what engine I have? If so, which ones and can anyone on here decode them for me?

2. If it is the 307 with 305 heads would putting 305 heads on there be good bad or indifferent to the performance of the engine?

3. If it is the 307 I plan on keeping it mostly stock but if it is a 305 I was thinking of maybe putting a different intake manifold, a 4 barrel carb and different cam. I already have a pretty good exhaust so what would you recommend for the manifold, carb and and cam?

Thanks alot for any help you might be able to provide. -Moneypit