sorry so long to respond. I'm not that educated about turbocharging so I can't comment on the cams but I think I have seen a post or 2 on some forum somewhere about someone that turbocharged a 4.5. Early in my project I did some research on having pistons made and then looked for some off the shelf ones that were close enough to work. The closest I got were Buick Grand National pistons-they are about 97mm, close to the correct compression height (take off about .09" off the top to set the quench)but you would need custom rod small end bushings because the Buick pins are smaller-or machine the pistons for floating pins and use the Mercedes pins. They are actually ideal but for me it was easier to use the 5.6 pistons.
https://www.summitracing.com/nv/parts/slp-l2481f30/overview/?cm_mmc=pla-google-_-shopping-_-srese1-_-speed-pro
I would be happy if mine made 300HP-I don't think the heads are good for any more with the 1.75"/1.5" valves.