not neccessarily....most 283's will handle a .120 in overbore...corse you should sonic test your block first....

I looked in Jegs the vortec's can be had for $500.00 for the pair complete...add $100.00 for intake...

total rebuilding your heads with hardened seats may run you more than that....

with the Vortec's you have slightly more compression and better cylinder and combustion efficiency....that means more power and better mpg doing it.... most cost efficient!