I don't feel the 3.5 collector is the right set-up for the OP's combo.

Ideally, I would want 1-3/4 > 1-7/8 stepped primaries with a 3" collector for that combo if I had the choice.

IMO, the 1-5/8 primaries and w2 heads doesn't make any sense.......well...... Maybe on a 318.

68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads