I'd do a little reseach on Pontiac Bonneville, Olds eighty eight,olds LSS and Delta 88 they are all the same platform (h-Body) the bonneville and olds LSS were ''sport'' models so you might retrofit some parts from them, and maybe even take a superchager from them if you are lucky enough. But as they told the 3800 must have an aftermarket for it..!

otherwise take a look on ebay always a good place to take a look