Although I have installed a few CF clutches over the years without issue, mostly in import 4x4 trucks, I am not a fan. I just think the weight design is cheesy. I think a swap to a McLeod or Ram, I like McLeod better but only a little, is a good move. Long style or diaphragm, they both work great, I have one of each in my 2 vehicles
As far as the spacer, when I did my TKO swap, I used a Dark Horse crossmember, and I deeded to raise it about 1/2 inch. Look close at the vent in the front, it likely will take a whack of the hammer on the floorboards to clear, and honeslty, if angle is right, I do not know how you can avoid cutting the seat cross brace unless it is one of the modified transmissions for that purpose. I proudly cut mine, it's no big deal, you just notch it
As far as angle, don't trust anyone, it should be 3 degrees down compared to the frame, and the pinion should be slightly steeper 1-1.5 degrees as an estimate, as the pinion will rotate up and needs to be parallel during acceleration. Use a cheap angle checker or with an Iphone you should have a compass app that has a second page with angles