I have good news for those of you considering this mod for your 65/66 B-body; the GV unit will fit without cutting the floor
with the changes I made to the xmember and by removing a portion of the front seat brace. Keep in mind that I am using the short tail shaft th400 from an A-body goat. Here are some pix of the modified xmember, underside of the floor mod to the seat brace, and the resulting trans hump clearance. I wound up using the Mustang 6 cylinder motor mount for my trans mount. Also I moved the xmember forward 1-1/4 inches. I'll send more pictures later when I repair my floor trans hump. I pulled a muscle in my neck so my work is on hold until it heals up.