$100 is fine.
I never seen a head crack in a slant, I have seen a block crack from not having Antifreeze (Winter). The owner still drove the car home with the block weeping and parked it.
As far as building a more powerful engine, do not invest a lot. After playing with slants for a couple years my best advice
Clean, gasket, ring
Mill the head .100 (yes you read that right)
Oregon Cam Grinders - copy the hyperpak original specs
Be careful of the 80's slants, I believe they went to hydraulic lifters and cast cranks. I'm not entirely sure if they kept the adjustable rockers, but these need to be lashed frequently.
The other best money is an HEI upgrade and a good 4 barrel. This all should put you at your 2k budget if you do the work.
