Hi M!ke, one thought about those Hall headers. Before you pull the motor (but have the existing headers off) I'd test fit BOTH Hall units to see if they line up properly. Mine certainly didn't.... off by 1-2".... which required much painful tube cutting & welding . There may have been more than one Hall header design down through the years but the set I got - cheap as it was - was no bargain!
About the jackshaft, as long as you take the front pulley off, you can pull the motor without removing the whole jackshaft assembly. That said, you'll probably find insufficient clearance for sliding the pulley off the end of the shaft unless the powertrain is 'loose' and angled or moved a bit to make space. I was surprised how tight things are at that end of the jackshaft....on 1010 (w/ non stock manifold) I've never had any luck installing a fully assemble jackshaft back on a fully mounted engine....just not enough space. Always need to install the front pulley 'mid-assembly', one way or another.
Good luck with the project, be interested to see things come back together! Regards, Nate