for 200 you can get some new vforce reeds
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for 1200 you can get a trued and welded crank, porting, new pistons, coolhead with higher comp domes, advanced timing plate, and possibly reeds.
how much time is on your crank and how long do you think it will go? typically a stock crank will need to be trued and welded before it can reliably make a good amount of power without separating. If you want to put money into it without knowing how much time is on it, you may be gambling a little. Buying a new crank would be ideal to know you have a 0 hr crank. if your going to buy a crank you might as well go with the 4 mil because it gives a mechanical advantage with not only the longer rod but its pin is 2mm outside of the centerline of the crank. with this advantage and porting the cylinders to match the stroke it can be a long lasting 70-80 hp motor once tuned in.
Boring a set of cylinders to the max means that you cant bore them any more. that means that if you do port them, then once you wear that size out, they are trashed or ready for resleeving. A big bore resleeve is typically 150 per cylinder and 90 or so for the sleeve each. If you have the money.. do both. or better yet get the 4mil crank and a 421 cub topend. but then your looking at a more of a drag motor.
get a hotrods 4 mil crank and have stock cylinders ported for the stroke and measured for new pistons. no point in boring unless you need to go to next size for correct piston wall clearance . then sell those domes and have some cut for a 4mil on whatever fuel you want to run. I can usually build one in the 1500 dollor range