99 5.0 GI Volvo Penta siezed

[Lou C]

I'd be more concerned with This,.....

Odds are, yer transom is rotten, 'n needs replacing,....

This needs to be repaired, before a new motor can be installed,....

Agreed this is the most critical issue as I posted a few posts back. As far as 5.0 vs 5.7 the only issue to be dealt with is the fuel system; if it’s a carb the carb can easily be rejected for the larger displacement but if it’s a throttle body FI then that is more complex. Check the transom as I said above.