The lack of performance parts when they were new and a few years old is the big issue for them. Now, there is a few more things that you can get and it starts with the big helper in HP, headers from tti & a new intake is available from Chrysler Power. Camshafts are not a problem today as well as most anything else you want for a high performance engine to a light drag car.
As noted earlier, pistons are custom and pricey! Speaking of which, where did you get those slugs from?