Headers vs. manifolds
Please describe "Warmed Up." With the parts being used. Do so include the trans type, stall converter speed if so equipped, rear gears and the tire size.
IMO, and having been there and done that, there are two routes to travel for headers.
1: Cheap typical headers and a Summit/Jegs dual exhaust.
(Not really the recommended route.)
Edit -> Though I do like the Jegs & Summit exhaust kits a lot, not the typical 1 size fits all header.
2: Dougs headers or a full tti system. Both of which do not drag on the floor. Fit excellent. TTI exhaust required minor trimming to fit the wife's '67 Cuda.
Pricey but very well worth the expense hands down.
Sorry I can not help with the exhaust manifold issue's.