I just traveled down to Knoxville TN to see my dad, and find a truck. I was unable to fin anything pre1999 with a 5 speed. We went all over about 10 counties in all, and never saw any 96's or 97's. and the only 98 12v were auto's and very expensive. While looking over the few 24v 5 speed trucks, i noticed a few things about the blocks

1 had a 53 casting, a few had no numbers there at all, and 1 had a 55 casting. For future reference, that ones that had no casting numbers, on the lf lower bottom, are those replacement blocks?

Thanks

 

I think those were the good blocks...replacement blocks would have the "same" markings as a factory block.

Chris

 

In response to Chris' comment, not necessarily. I don't know how often it happens, but I know that HaulinInDixie (on this site) had the "53" block problem and got it replaced (I forget whther it was under warranty or not). The replacement block cracked also, just out of warranty. He found out that it was also a "53" block but someone had ground the "53" off the block.
Nowadays I'd suggest you find any numbers possible on it and research them. Look in the typical places on the block and see if you can see any sign of grinding. They certainly will pain over it, but usually it will be rougher, or will have multiple planes on it (if the grinder tilted the wheel while grinding it. This is typical when grinding).
What I klnow about the locations on the block: http://www.Stamey.Info/Truck/Cummins53BlockFAQ.htm

I hate to rain on the party, but you should be aware of the potential pitfalls.

Chris