SBE 318 basic rebuild +CAM , INTAKE, HEADS, expectations?

Hi team
lets me start with thanking all of you for the patience and the knowledge you provide.
great stuff.

so i had a couple other posts where i mentioned the 74 Duster 318/904 car i got and the different possible routes that i considered to go.

i checked on the OEM engine and its a runner with good compression ( all Cylinders are max 8psi apart and between 107-115psi , with a generic compression tool which i believe is not the most accurate ).
I am in the process of pulling the motor and trans and "REFRESH IT" with new gaskets a good clean. and i want to throw some "performance " parts on it.
i will do :
-dual plane intake
-a Summit cam kit ( since i live 10 min from a summit ,it is easy) SUGGESTIONS? https://www.summitracing.com/search...10RPaH8Xo5ULd6G0s4ZbAGija3CBgsV2p9FQ8rXqB0vND
- Carb: most likely a Holley Vac Sec. 650 or 750

and the Heads:....
Yes i understand that the OEM heads can be rebuild and upgraded, however by my experience i will run into , Cleaning , valve job , Springs, seals , milling , probably loose guides etc...
+ i would consider Port work since i have the "plug" in the Neighborhood ( elliotsportworks) so its a BILL of 600 + $ no matter what and its still CAST heads.
by that time and $ , out of the box alu heads become reasonable i think

So the questions is basically
what performance gains can i expect from simple SPEEDMASTER or PROMAXX as cast heads for FT Cams ?
I would use the stock Shaft rockers

I have a set of longtubes on the car already that i can most likly refurbish as well and use..