Welcome to CHR guys!

Love the father son projects!

As Pat stated, the $1000 budget limits the top end build however; we can help you get close. These Vortec heads don’t look too bad for $680 and they have no core and free shipping – see New Chevy Performance 302 350 906 Vortec Cylinder Heads | eBay
Specs:
64cc Combustion chamber
185cc Intake runners
2.02 Stainless steel intake valves
1.60 Stainless steel exhaust valves
Straight plugs
Assembled with hardened keepers and retainers
Springs good to .600 lift
Assembled with 3/8 screw-in studs and 5/16 guide plates
Heads are assembled with new valve seals and are ready right out of the box.

Summit cam and lifters - $89.00 - SUM-K1104, duration at 050 - intake/224 exhaust, about as big as you want to go without serious internal upgrades. If he’s running a four speed this will be a great cam. If an automatic you’ll want a 2,000-2,400 stall converter with 3:73 gears to get good results in the Chevelle (it is a heavy car). Summit SUM-K1102 brings the duration back to 204 intake/214 exhaust at 050 and that is very “streetable” with a stock automatic, stock converter and gears.

Look on ebay or Craig’s list for a used Edelbrock Performer RPM – usually about $75-125. Make sure it’s for Vortec heads! 7116 for square carbs, like the Edelbrock 1406 and 7104 for spread bore like the QuadraJet. This will put you over the $1,000 – but you should be able to pick up a used 1406 for less than $200. I’d stay away from a used QuadraJet unless you know the source very well. I like the Q-Jet a lot, but they can be tricky to rebuild and initially setup. Once dialed in, the Q-Jet is an awesome carb. The 1406 Edelbrock is a 600cfm unit, electric choke and real solid. May be a bit rich out-of-the-box, but re-jet is simple and inexpensive.

Heads $680
Cam/lifters $89
Used manifold +/-$100
Carb +/- $150-300
Gaskets and such - $100

So, realistically, for $1,200-1,300 you can probably accomplish your mission.

Good luck and let us know what you decide!

Regards,
Glenn