You're better off buying a good used running 1G than trying to piece it together.

By the time you add up all the incidental parts, shipping if any, time running around, parts to rebuild the engine or tranny, etc, it will definitely run way over what you have budgeted to build the car.

Now if you just go throwing a used engine & tranny in there it can be hit or miss, the engine could be worn out, the tranny might grind after being installed, bascially unless you know what you are getting its still a big risk.

You buy a good used running 1G you can hear it run, drive it, check it out as a whole, do your mods and race it. At least you'll have an idea of what you have from the start without going through months of bs piecing the car together only to find something isn't right.