5 liter MOPAR

So sometime in the late 50s, early 60s Chrysler wanted a car that could be run in a 5 liter class, so they built a 301 poly engine and offered it to the general public in the body they wanted to use. This was a short stroke 318 poly. The only change that you have to make to use it in an LA motor was it had an 8 bolt crank like a hemi, so you needed a hemi flex plate or what ever the conversion is for a 4 speed. In the 1980s a machine shop that I used made dirt track stock car motors out of LA motors with these cranks. Since no one builds polys to speak of these days you might find one cheap. I believe they were forged cranks.
Right. All of the polys had forged cranks as did most of the 273 LA motors. One of the reasons for the LA motor was to cut weight. I think a cast crank is okay to about 650 HP. i don't expect more than 500-510.