3406B in a 1995?

It could be original, most confuse the last mechanical C models with the B models. If the engine serial number is 4MB or 3ZJ it's a C. Easy way to tell is if timing cover is more pointed and has eight bolts it's a mechanical C

 

94 had Emodel in it.

 

The E and the mechanical C were both used in 94 and 95. If it was a mechanical C from factory that has a B in its place you may have the emissions issues you were concerned about

 

you will be able to get the B model into the acceptable emissions range with some tinkering of the IFRC valve on the fuel pump. But if the motor doesn't match the tractor it does raise some flags. Something to look into.

 

I ordered a new 379 in 1994, technically a 1995 year truck with a b model cat

 

could have been a 94 left over titled as a 95. dealer could do that back then if the truck was not sold that year. my 71 pete had small windows,some guys claimed 72 was the last year for the small windows,wrong they were 71s titled as 72s. i am not sure what year they stopped doing that. plus you could buy a 1693 ta cat motor,hands down one of the best motors ever made for a truck,but you had to like a noise in you motor,i am sure wore out knows about precup injection. be safe out there

 

It may also be a case of starting life with an early version of an E--and after it was used up--instead of rebuild--found/had a good B and made the swap---remember in the early days of Electronics--many of us were not nearly as tech/computer savvy--and no matter if the motor was good or bad--we were somewhat uncomfortable with the electronics...and if givin a chance were happy to change---not to mention--at least in my world--a Bmechanical was quite frankly the most reliable--easiest to deal w/motor I ever ran...but thats jus me