How will it perform?

-Boosted- said
408

Solid Roller Cam - 660 lift, 258/264 duration at .050 108 LCA

Camshaft manufacturer? Cam card?

-Boosted- said
Thumper 950ish carb on a Victor 340 and HVH 1" spacer
Hedman Huster headers with 1 7/8" primaries and 3.5 collector

It might like more spacer, hard to call. So you have more to test with?
Header size is good IMO. Did you maintain the exhaust pipe at 3.5?

-Boosted- said
'73 Duster (3000# with me in it)
Caltracs
Calvert mono leafs
Calvert shocks front and rear
FirmFeel uppers and strut rods.

Have you run the car with this set up since the change?