The 392 is a raised deck version of the original Chrysler Firepower Hemi and as such has bore spacing 4.5625". It is a lot closer in design to the A/LA engines than to the B engines. A 426 Hemi is an RB engine, that's a B engine with a raised deck. Bore spacing is 4.80".
The only thing the 426 and 392 have in common is that they were based on a raised deck version of a previous block series, and that's a words-only similarity.
The other major pitfall for you and this engine purchase is that from the outside it is very hard to tell a 392 from the much more common 354 or 331. There is a code I believe stamped onto the top valley rail that will tell you what the engine is and where it's from.
Do a Google search for Chrysler Hemi and you'll find the chart. Lots of information is on the Web.
Now on to this particular engine - once you determine that it's a 392. Here are my top five reasons to buy a 392:
1. It's one of the coolest looking engines ever made.
2. You own an early letter series Chrysler and want to give it a boost in power.
3. You have a nostalgia dragster and need a 392 to make it right.
4. You have a spare '34 couope body lying around and want to build a traditional hot rod.
5. You have a big wad of cash burning a hole in your pocket and you always wanted a Hemi.
If you want to see what it would cost to rebuild a Hemi go to PAW or
www.hothemiheads.com. They ain't cheap!
For $3000 this engine would have to be guaranteed to be rebuildable, like pass Magnaflux and crank and bore sizes are within reason. Even a fresh rebuild would need to be gone through because there are good parts and crappy parts.....
Also I think that price is more of a speculative price, much like the $2500 barn fresh DeSoto or Dodge hemis I see on Craigslist every now and then.
Good Luck!
R.
100% 
and the WOW factor when you pop the hood is there 
... my 
