I just always thought that roller stuff freed up horsepower. And i could get a magnum motor around a hundred dollars. And use the spider roller cam and rollers lifter. And maybe the heads if it helped.
If you want a roller cam engine, then go seek out an '88 - '91 engine. That is when they had hydraulic roller cams and you can still bolt the LA intakes.
We're building a 91 360 for my son's 71 valiant 4 door. We got it half way together so far. Hughes cam and LD340 intake.
All I'm sayin' is that if you have a LA engine keep it as it is and have some fun with it. If you want roller, get a roller block engine and start from there. Trying to morph between the two can get complicated.