Scout, your measure sounds about right. The bare engine block is 29.45" long. The flywheel housing is probably nested under the firewall. The fan and fan hub assembly is all out front. With 38" there couldn't be a lot of room between the fan blade and the radiator. A tight squeeze. When they added the intercooler in '91.5 the fan hub got shorter. That was as compact as a 6bt got.

 

I took the measurements off of my 91.5 and my wife's 94. The measurements are plus/minus 1/2"?
In both trucks the engine is about 1" from the firewall as far as i can measure, and the fan clearance is about 1.5" to the radiator. These measurements do not account for the charge air cooler.