Hey folks,,,, this is probably been talked about before but I'm dropping a 360 Magnum in where a 3.9 was in my '87 Dakota. I have a 904 transmission I want to use. Will this work with this engine? What flex plate do I use and what torque converter do I use? I wanted to use a B&M converter that stalls around 2200 rpm. Is this combo good and a direct bolt in? Advice appreciated.

 

I'm doing the exact same thing....

First off are you rebuilding the 904? I'm putting all new red alto and Ray asbestos clutches and rings. The stock 904 may not hold up to the 360 torque.

In any case you can do this but you need to understand that the 3.9l was an internally balanced engine. The 360 magnum is an externally balanced. So your options are:

Use the 360 magnum factory flexplate with the weights on it and then you can use the 904 neutrally balanced converter.

Use a 5.2 magnum flexplate and add the weights with the weight kit to the flexplate or the converter.

Use a 5.2 flexplate and buy a custom converter with weights which is $$$.

If you don't have the magnum flexplate you can hunt around for a b&m 10242 for 727 or 10241 for 904. Both will work but the 727 version you'll have to elongate one of the holes. However both are discontinued and near impossible to find...especially the 10241 for 904.

If you have the factory flexplate you'll also have to elongate one hole.

Here's a good article covering most of this

http://www.magnumswap.com/automatic-transmission-details/

 

Points well taken! Appreciate the advice. My 904 has been thoroughly rebuilt with Cheetah valve body. I've done a few of these swaps before but never with a Magnum. Always used an LA motor. This time I wanted to build one that I didn't have to fabricate motor mounts. Also wanted to use this 904 that I put together. Others were 727's. I still may end up using this LA 360 from an old police car (E58) that's just itching for the stroker kit that's staring at me in the corner of my garage!! I checked out that web site on Magnum swaps. Awesome reading and really very simple to do. Now I'm armed with enough info to make something happen. All I have to do is get off my *** and make a decision!! Warm weather and long days are approaching and it's time to get out there and shut down these kids around my block with tuner cars and loud fart can exhaust!! Thanks for your input. Hope to post some pictures of the progress of this build very soon!! Until next time, Sports fans,,,, stay tuned!!!!