Thom,
The correct slip yolk for a T5 can be found in virtually any Salvage Yard.
The answers to your questions about driveshaft modification can only be given after measurements are made. as you had mentioned to me, you may need to shorten the front piece of your two-piece driveshaft approximately 15 inches. The correct conversion universal joint can only be determined once you know what the universal joint is that you currently have on your driveshaft.