Might be easier to do the topend on the 600 than to try getting the 500 into the sled and running.
You could always sell the 500 motor to finance the 600 rebuild.
If you go that route just be sure to identify and fix the problem that caused the motor to blow in the first place.
BTW, where are you located?
2004 MXZ 500SS - Son's
2000 Z370 - Daughter's
2003 Pantera 550 - Wife's
1998 ZL500 - Mine
1988 Springbok Bowrider/110 Johnson