Converter go to Pro Torque. I didnt and that was a mistake. They have a low stall HD unit - I think its $400.
http://www.protorque.com/
Shift kits from Superior, and Trans Go. These are valve body kits- drilling, springs etc. Some of the stuff is update items which you might not need. But you can tailor the shifts a bit.
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If you are rebuilding look for an alto "power pak" kit to increase the number of clutches. The superior shift klit also has better clutch apply springs - which may be standard in the 4r series (hear say havent been able to confirn it). If you cant get the power pack, updated waffle faced clutches, or grooved clutches are avail from Ford and aftermarket to increase holding power.
http://www.altousa.com/ib41756.htm
General rebuild ideas
address cooling during rebuild- more cooler & Bigger pan(custom) especially if you use a higher stall converter.
OD planet get a welded or billet piece.
Pay the money for a new pump from Ford.
Make sure they check the bellhousing and align the housing during install. Check the crank bushing. All to prevent the dreaded front seal blow out on rebuilds.
Found this article on the web:
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added some links on edit.