Those two bolts will haunt you.......
Work on the one near the alternator.I do not reember how we got it off but finally did.....then you can slide the header out of the way a bit to get at the other one.
Just a bit of wisdom here.....go get longer bolts for the flange that goes from spipe to header as it is a night mare to get the ones they send you on.Also pull out the tranny lines,fans and radiator.....
Install header from the bottom of car with the pasenger side of the header facing up and rotate it around to vertical and it will go right in.
If you leave the lines and radiator in you have a 50/50 chance of popping the radiator which is a lot more expensive than tranny fluid and antifreeze.
Good luck with those two bolts.
Build it like you dream it.....