Can it be done or is it best to get already 4 bolt main?

 

Get a four bolt, unless your making less than 450hp and a redline below 6,500 RPM then a two bolt is fine w/ main studs. These numbers are conservative, I have built a few two bolts that have withstood more power. The cost of converting will be about the same as finding a used four bolt, maybe a little less. If your looking for a two piece rear block look for one with 010 and 020 under the timing cover these will be the best for many reasons. If you need a one piece block look for a 880 on the side of it, these are the later design roller blocks used in Vortec trucks and ZZ4 crate motors. I like to avoid the early one piece blocks in my experience they seem to crack more often than others, but I'm sure some live a long life.

 

sorry about jacking the thread, but is a two bolt spalyed to a 4 bolt stronger than just a regualr 4 bolt?

 

The cost to have it done could easily amount to the cost of two used regular four bolt main blocks.

 

as far as i know its significantly stronger

 

It can be done, and is usually far stronger to do that, than to use a factory 4-bolt setup. Aftermarket main caps are usually steel instead of cast-iron, and have the outer 2 bolts in each cap at a different angle from the center 2, which gives better load distribution from the cap to the bolts to the block.

A factory 4-bolt setup is somewhat stronger than a 2-bolt one. That's why the factory uses it in truck motors.

The next question is, does any of this matter for whatever you're doing? Chances are, if you're asking this question this way, it really doesn't.