Sounds like you have a good plan.
Don't know the axle measurement on your 46. You can get a close guess without removing the wheels, think a little.

Just a quick search on transmission coolers turns up these finned coolers
http://www.makcotransmissionparts.com/Allisoncooler.html
Note that some are stand alone with an electric fan. I've seen hydraulic oil coolers the same way on construction equipment and trucks with hydraulic cranes and things like that, one of those would do as well.

Roadranger has a number of coolant options, some are remote mounted water to oil heat exchangers. These will get you started thinking
http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/rr_apsl-0021.pdf
http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_065654.pdf
cut and paste I guess..

Last edited by Grigg; 10/24/2012 4:31 PM.
•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
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-