I dont have headers so not sure about those, but swings and roundabouts really on whether to put box in with engine. Luckily those gearboxes arent TOO heavy to lift in from underneath.
Engine in first install
protect the firewall because when you drop the engine on the mounts it will want to fall backwards into the firewall, denting it or damaging engine, so devise a cunning support with wood, cloths and stuff. You want it tilting back a bit to make gearbox go on easier. make sure torque converter is properly engaged in trans before tying to install it, and make very sure not to let the TC fall out when you lift it in. A trolley jack and a piece of MDF make a reasonable gearbox jack.
Engine in with gearbox install
jack the REAR of the car up as HIGH as you can get it, this makes the rad panel lower, and makes the tunnel higher, perfect angle.
wrap blanket or cardboard etc around top of gearbox to stop it scratching the tunnel
try to borrow an adjustble thingy to change angle of engine while suspended as u need it at shallow angle to clear rad panel, and steep angle to get the box under the tunnel.
Bribe your mates with offer of beer to come and lend a hand.
When the engine is in, it is customary to run it up once without the exhausts connected. This is becuase it will sound bloody awesome.
good luck!
