It's duration that uses up clearance(amount of lift at TDC).
On a stock 400 that has the pistons down the hole .080+, and heads that havent been cut a bunch, pretty much any cam with less than mid-230's @.050 should fit okay. So, anything that's "appropriate" for the rest of the combo shouldn't be a problem.
The only place where lift might be a concern with that build and stock heads is retainer to seal clearance.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
