i have a 64 el camino it came with a 300 horse 327 4 speed my friend will sell me a 375 horse 327 short block out of a 65 vett my question is will a set of vortec heads or edelbrock e-tec 170 heads be a direct bolt on or what do i need to factor in to make shure they will work. im getting the motor cheap and im on a tight budget also i dont have the 300 horse 327 or i would use the 461 heads that it had. what cam should i use. and how much horse would you guessamate?  

The vortech heads are a direct bolt on and there are some redrilled for old school intakes though the have a warning about deck hieght on the gmpp site concerning potential intake leak I think the tock ones need a vortech style intake and the temp sensor is smaller but the heads are a direct bolt on.  I'm no help at cam selection, since there are variables most will want like gears and stahl if auto and what not I go by the philosophy that the sales department for the cam company knows best as they work with them daily.  Sounds like a nice elco, good luck.  

Like the other guy said the heads bolt on just like every other small block chevy head. However for the factory vortec heads have limited ability to handle lift (about .440)and need the self-guided type rockers. the E-tec heads have no hangups unless they need the vortec specific intake too.

Your output is directly reflecting your cam and exhaust. If you keep the bottom end stock(375hp 327) its going to be around 11:1 compression(does it still have the domed pistons in it?) So for cruising your going to want a high overlap cam to stop detonation. (or run race gas mix or octane booster) 425 horsepower is doable with a performer rpm manifold and the right cam, But it is gonna be peaky and unless you have 4.11's or 4.56's not too much fun to drive. (especially in traffic)

The Vortec heads will bolt up fine, and you will want to use an Ebrock Performer RPM air gap intake to match. The cam will have to be below .500" lift, unless you use the high lift versions, then you'll have to keep it below .530".

As far as the cam, I'd go Hyd./roller, but to spec you a cam, I'll need more info, such as gears, weight, trans,planned use, etc...so let me know on that. One more thing, with the 64cc chambers, you'll have a sky high compression ratio, like 11.25:1, as I recall, the original heads were 76cc chambers.
You will need some high octane fuel, maybe some octane booster as well.