25/30..going to do it, do it right. You will love it.
keep your head. Sell your bottom end for a few hundred.
Pick up a rb30 for 100 bux. cheaper can be found easy enough.
depending on power, forged spool rods for like 800-900bux should pull it up or can use standards, forged pistons for like 1350.
new bearings maybe 120, thats mains and big ends. headgasket for like 200 or less.
Just machining($1000) and assembly(fark knows, never paid anyone to assemble a motor before) required.
Exhaust will need to be modified, and ic piping, if using std inlet you might need to drop the crossmember down a little with some spacers or raise the bonnet.
There is a little bit of work involved, but if your not afraid to turn some spanners and get your hands dirty, not only can you save some money you might learn something.