Block heater questions

So I ordered a couple of the kat 30208 block heaters.   I needed one for a 185 we are working on.   I also thought I'd get one for my 190xt. I never looked at the block but my block is not machined for the flange of the block heater.   No big deal I'll put it on my 180. So I'm wondering if anybody knows if any other style of frost plug heater will work in a 190xt. Also wondering if there is an aftermarket source for the block heater on an f2? Friend of mine who bought our old f2 is looking to replace it. Seems like I looked into getting one from agco once but it was pretty spendy. They look the same as the 30208 heater other than they have a tube coming out that is routed you the rear of the engine and is hooked to a hose.
Thanks

Forgot to add this; on the center hole there is a shoulder in block that keeps plug from going in to far. "Do Not try to drive it into block for removal. 

HagerAC wrote: My 190xt does not have the bolt holes or flat surface for the 30208 type heater, that's why I'm looking for a different style of heater that will fit into the frost plug hole in the rear.

I recently installed a Kat's P/N 11618, 600 watt, 35mm frost plug heater on my 1968 190XT.  I made the butterfly wings as narrow as possible, lubed the o-ring, inserted the element at about one o'clock and torqued the machine screw to 15-19 inch pounds. It was a nice snug fit w/o any modifications. I didn't like the five foot cord that came with it, so I bought a Kat's P/N 28201 one foot cord. Be sure to use some very fine sand cloth to clean up the hole where the o-ring seals. Around here, Auto Zone has it listed for $25 on line.