My advice would be to attack each project one at a time. Neither of them are a "go out and throw it in" kinda project. Either looks like a good summer project, not both.
I wouldn't even BEGIN to worry about tire size right now, that is the last of your concerns. You attack lifts and tires sizes in one of two ways: 1) You want to run this size tire, and you lift it to corfortably fit those tires. 2) You lift it as much as you want, then figure out the biggest tire you can run comfortably.
Personally, I would attack the SAS first. The SOA in the rear should give you about 5.5". BUT, you will probably find that you will need more lift than that for the front driveshaft, and other stuff, to clear nicely. This is why, when you read through the SAS threads here, that the final lift is MORE than enough to clear 35"s and 37"s. You will see people tell you how they now have 8", 10" or even 12" of lift. My SAS plan was to only go up about 6" (to match the SOA), but when said and done, it is prolly in the ballpark of 10". When you look at how much lift if created by doing a SAS, adding a body lift to that starts to look frivolous (and more dangerous). Also remember, that when you get into an SAS, you are looking at a ballpark price of $1000-$2500 just for the parts needed. Then you get into expensive tires, re-gearing, and lockers. In the end of it, you will prolly have $3000-$4000 in it (no labor, which will be A LOT).
Can't help you with the V8 swap, I know nothing about them except they get expensive also.