I'm planning to change the t90 in my cj6 to a t15. Knowing the D18 had a small input bore, and the T15 needs the bigger bore, the question is, has anyone modified the bore of an 18 to equal the 4in bore of the D20? I have a spare D20 on hand, but I hate to use the only one I have if the d18 can be bored. Pros/cons anyone??