Looking for advice, BB headers vs. HP manifolds

I continue to pick the collective brain pool here, as I work on assembling a Big Block 69 Dart. No car yet, but I'm gathering parts.

The engine is a 383 intended to be nothing crazy. I want a fun street car with good manners and improved performance from stock, running on junk gas. It might hit the strip once in a while, but mostly it will be a street car with more emphasis on handling than straight line speed. Shaving weight up front is one of my goals. I plan on an aluminum intake, water pump housing and pump, and heads.

It will have manual brakes and steering and a 4-speed. Unless I am completely mistaken (always a possibility in my world :eek:), headers will offer the best performance. But in an A-body, there are issues getting them past the Z-bar. TTI appears to be the best fit option, and they do offer a modified Z-bar to help with fitment, but we're talking somewhere around $1000 or more for this setup.

A guy local to me has a set of B-body 383 HP manifolds for sale somewhat reasonably (asking $375). From reading on the Big Block Dart site, it appears I can fit these in an A-body by cutting back the steering shaft surround.

The question for the group has to do with performance and trade-offs. I think headers will give more performance but at higher cost and with fitment issues. Manifolds will likely fit easier, but probably weigh more. Would HP manifolds be a sufficient performance part for my build, or should I just wait and pony up the bucks for TTI's?