Let us know how it goes putting the engine in with the headers on, i'm bolting together a 383 also and i have the Schumacher headers for it and i was wondering if i will be able to put the engine in with them bolted on.
it will drop right in. i installed my engine/tans combo with the headers installed. i just pulled the steering column out and it all dropped right in. i put the car up on ramps in the front and had my dad lower the engine in while i was under the car tilting the trans down. just go nice and slow. it will all fall into place. I also recommend leaving the motor mount bolts loose on the block. drop the motor in and then snug up the bolts. that allows more "wiggle" room.