28'sonic
 

with single 502 what type of speeds would i see if i added a procharger.Also is this a true 28'er or is it 26' and another 2 feet for the swim platform?

Its a 26' boat with a molded in platform. Not sure if it has a notched transom, but it probably does.

The boat might run 60 as it sits right now. I'd venture to say maybe 70-72 or so with 600HP.

My 1999 26' Sonic was 72mph on its best day with an HP500EFI; 512HP at the crankshaft/470HP at the propshaft.

Personally stay away from the 28 (again personal choice). I would go with either a 26 with a single HP500 or a 31 with twin HP500's.