Here is a great thread about the T5 swap and the required steps to switch the spedo gear, with great pictures too.

on the OldGMCtrucks.com site
http://oldgmctrucks.infopop.cc/eve/forums/a/tpc/f/633004236/m/4141096923?r=5031090133#5031090133

Grigg


1951 GMC 250 in the Project Journals
1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-