Dorfan engines

Twist Ties make everything couple together.  And many here change out couplers to couple different brands together.  Tom Snyder asked Mike to make a "Universal" coupler for Tinplate, but so far, no go.

I do know that the TCA "GRAMPS" MTH-IVES tank came with both Lionel and IVES couplers.  Don't know if there are other examples.

Sunrise,

I know for a fact (because I own a set) that the Dorfan passenger cars from MTH have the couplers held on with a single screw.  You have to take them off to put the cars back in the box.  I would assume someone could easily change them to another coupler if desired.  You may have to drill out the hole on the "foreign" coupler shank to fit the screw, but otherwise they should fit.

I have no knowledge on the locos, but where there's a will, there is a way!

Sunrise, there are, of course, Dorfan wide gauge freight cars which have the Dorfan couplers, but they are vintage only at this point - lithographed beauties - MTH has not attempted a reproduction.

The closest thing to a universal coupler is the old hook and slot, like on the Lionel 10 and 100 series freight,  before the Lionel latch coupler.  Also used widely by McCoy, CMT, and other modern standard gauge makers.  The O gauge version of this coupler really was a nearly universal coupler at one time - Flyer, Ives, Marx all used it and thus are all compatible with each other.  

The standard gauge hook coupler is readily available, cheap, works great, and is easily changed out on most if not all standard gauge.  At one point I seriously considered changing everything over.  But once your collection reaches a certain point, it ceases to be an issue.  

Dorfan are enough of an oddball that unless you really like their cool quirkiness, they would be a prime candidate to change out to your preferred coupler.  Easy to do if you can turn a screwdriver.

Thanks to all for the great information!

Sunrise