Whats the diff between a Hemi block and a RB block?

[Hopalong]

This may be a dumb question, but what is the difference between the blocks?  Head bolt retaining?  I could see bore size being different, but any other internal parts?

[426 pentastar]

the biggest difference is the main caps and the way the motor mounts bolt to the block.there is alot off difference between a oem hemi block and an rb block

[Chryco Psycho]

actually there are a lot more differences that cause problems the oil return passage back from the heads is not present on the 440 block , the deck is notched quite deep beside the cylinder bore to clear the exhaust pushrods & the upper row of head bolts which are in the same position as the RB cannot be installed as they bolt would pass right through the middle of the intake port , the hemi has studs installed in the head under teh intake ports that drop through a Boss in the lifter valley , nuts are threaded on these studs from in the valley & troqued from below the head , none of this is possible with a RB block
Stage V engineering made a conversion head for the wedge block that has a short head bolt installed inside the intake port & an external drain for the oil into the pan & a template to notch the block for pushrod clearance 

[Hopalong]

Thanks guys!  I knew about the hemi head conversion and wondered why you don't see more of them?  I have a 440 that I am excited about puting together but started thinking about options.  Right now I am leaning towards a stroker kit.  Has anyone here dealt with the guys from www.440source.com?  They look like decent kits and the price sure looks good.  Am I missing something from there site?

[Chryco Psycho]

decent Products & good service from 440 Source , get the rings & brgs for the $200 extra , they will cost more from anywhere else that I can find