Offset or not, it makes no difference. (till you calculate total universal joint operating angle)
The most important part is having the centerline of both the transmission and the pinion be parallel.
Basically you put the engine wherever you want, but be sure the trans output shaft and the pinion are parallel

This tech tip has links to manuals that will explain it all in detail.
http://www.stovebolt.com/techtips/driveline/setup/index.html

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-