I'll assume the T5 you have is ready to use as is.
The bearing retainer on the front of the T5 case fits snugly into the big hole on the bell housing. The hole and bearing retainer should both be 4 + 11/16".
You can either remove the bearing retainer to cut it to the proper length or you can slide a piece of protective material between the shaft and the sleeve so you don't nick the shaft with your cutting tool.
That adapter plate on eBay is fairly thin so the bearing retainer will still insert into the bell housing hole enough to line things up properly.
