Cam & head upgrade 360 mag

Getting Magnum heads with the LA intake bolt pattern does open up the number of intake available. What you need to keep in mind is the port opening for LA and Magnum are different and will require port matching.

You need to build for torque. 400+ft-LBS is gonna mean more then 400HP. I think the cam you are considering is appropriate. You will need to verify retainer to guide clearance.

A good converter makes a world of difference and converting your 518 to non lockup opens up a world of 727 converters you can use. I re-used my 9.5" Edge racing converter from my 904 in my A500 I had converted to non-lockup. The deeper first gear over the 904 was a plus.