I have the same basic boat just a little older and with the 4.3 4bbl engine...it's a great running boat and it should fly with the 5.7...in fact if I ever re-powered mine I was thinking of getting a 5.7 since the price engine wise is not much more but since you have to change the gear ratios in the drive I'm thinking that might be the time to either do a Volvo SX conversion (only if I could get the drive at the right price) or convert the whole thing over to a Merc Alpha...
mine was pretty trashed compared to this one and I re-did the whole interior and replaced the deck as well...
I can say this hull design handles big water very well for its size...
The main things to be aware of is that the Cobra is a good drive system but it's not that easy to find mechanics who know how to adjust them right...and certain maintenance jobs are done differently than on a Merc...for example filling the drive for one...
http://support.crowleymarine.com/category/128/this link has some of the maintenance procedures if you don't have a factory manual....
http://www.hastings.org/~stuart/cobra/this link is the definitive piece on the Cobra drives and how to get them shifting right...
mine had a shifting problem in that it would not come out of gear easily and I took it to a local OMC mechanic he got it shifting right and it's been fine for 5 seasons since...we found that you can get salt deposits built up behind the bellcrank in the pivot housing so each season I pull the drive and clean out that area and grease all the pivot points on the shift linkage with OMC/Bombardier triple guard grease...the other factor in getting it to shift well is to get the engine in a good enough state of tune to idle in gear (on the water) at about 550-600 rpms...the slower the better....