Looking for advice, BB headers vs. HP manifolds

It's been a while but I remember the b engine in an a body with the Schumacher tri y's fitting as nice as a small block. Yeah the engine is taller and wider but the exhaust exits higher and maybe not as congested? Running the TTI 1 3/4 headers with a b engine would it really be much tighter than a small block with TTI headers? Keep in mind I may be in slight denial. Going from 340 with hp manifolds to 451 4 speed and not a 100 percent sure that's a great idea. I think the Schumachers would have more room than the manifolds and be easier to work on. I am planning on going TTI 1 3/4 headers. If TTI's shorty is as nice as Schumachers that may also be a nice choice over manifolds. Hydro clutch seems to have more clearance big or small block when headers are used.