LA360 or Magnum?

Tanis,
The strength/hardness difference between LA and Magnum 5.9 blocks are up for debate. I prefer the Magnum, obviously, but also because they have much better gaskets, roller cam and much less wear in cylinders which may be due to block or more likely, hyereutectic pistons, moly rings and FI. The Magnum 5.9 rotating mass is lighter too. Better rev for autocross.

The shaft mounted rockers may be stronger in extreme lift cases but I have never had any issues with studs, rollers and guide plates. Stud mounted are the most common type to cross the finish line on any given race day all across the country.

You can use the LA V belt stuff if you want, look at magnumswap.com if you havent already, it gives options for installing them either way.

I used to auto cross in LA in the 80's and miss it. Building a 69 Dart HT for Autocross and Roadracing if I can only find the time....PM if you have any questions about building for A X