If you are serious about doing it, put the ST205 running gear in, here is a quick guide......
Step 1: Buy a grinder.
Step 2: Buy a ST205.
Step 3: Use grinder on both cars.
Step 4: Buy a welder.
Step 5: Weld bits cut off ST205 into EP91.
Step 6: Try to drive it.................keep your fingers crossed.
Step 7: Have an epiphany, scream "fuck that" and buy a EP85/95.