360 build ????s

Alright, i have been assembling the motor. My main worry was piston to valve clearance. Well, that is the issue. Here is the full combo.

318/4 speed/8.75 with 4.11 gears
Stock rotating assembly
Purple shaft 284/484 cam
J heads that have been ported, milled .100, and the large valves installed. I bought the heads at a swap meet. Lack of knowledge and didn't see the milling job.
Stock length push rods and rocker shafts
Head gaskets are Felpro from a full gasket kit from Summit(number on the gasket is 8553PT)
Torker II 340 intake

What are my options with this setup? I am keeping the cam and intake.

I have read and been told thicker gaskets won't get it done. True?
Spacers on the rocker shaft???? Seems odd but an option?
Shorter push rods
Best to go with different heads??