Louis,
I just got home from MATS and I'm TIRED!
Cut that byatch up if it's what you want to do. 9 seconds ain't hard to do nowadays with boost/superchargers, juice... There are a bunch of guys running high 8's low 9's on leaf springs and 451-500 inch mills, some on juice. One Duster goes 8.75 at 158 with a 470....
Also... more than 1/2 the time when I see cars for sale that are partially done, most of the work needs to be redone to the way the new owner wants it. It's a crapshoot buying one like that unless you have someone that can look it over that's versed in chassiswork. I've got two friends that bought cars that were basically done and they were TOTAL JUNK. Everything had to be cut out and redone.
My friend got some pics of a SWEEEEEEETTTTT 70 B5 Blue Swinger from British Columbia that sounds like what you want to do. It had some HUGE MT sportsmans on it and the backseat was in the car with a FULL TUB.... It can be done, you have to get creative.
I had a buddy in the 80's that did backhalf cars in his garage... they ran hard, straight and the tin work was very good. It's easier on a jig, not impossible. Measure twice, think about the cut, measure twice more just to make sure! One of the members does his own ladder bar installs in his garage, using the leafs as a guide... Car goes ARROW STRAIGHT! It's all about getting a true centerline and pulling perpendiculars from that line.