Early Abody Doug’s 450 header install BEFORE engine going in

AJ, those early A headers have slip joints and flanges.

I think you'll be fine putting them together laying them in, just like you would manifolds. As long as the steering column and torsion bars are out/slid back.

AJ, here's a pic when I was painting mine. Which lasted about 10 minutes. I wrapped them after that.

IMG_20191224_145057.jpg