190 d19 rear end and axle housings

The D-19 rear end housing evolved into the mighty One-Ninety rear end housing. While they may look nearly the same, they ain't. The biggest change was the fact that the ring and pinions are different and this includes the pinion bearing bore in the housing. It is larger in diameter. The axle sleeve housings are the same as are the axles, although 190 XT axles are heat treated more for strength where D-19 axles are not. D-19 bull gear and bull pinion gears are different and a different ratio (faster).

I'm sure the D-19 and old One-Ninety axles have a certain degree of heat treatment, but part of the small axle "XT" update kit included new axles of the same 2 3/4" size that were supposedly heat treated better for more strength.

A four-pinion differential required a different ring & pinion gear set, as the two-pinion ring gear I.D. is too small and will not fit onto the four-pinion case. Maybe a good machine shop could mill out the inside of a two-pinion ring gear ??

A 200 ring and pinion and some of the trans parts do not interchange. Would have to use 200 main hsg and parts inside of it.

I think so. Haven't done it myself, but I think so.

Gearing is essentially the same between any age 190XT ( including prior to s/n 9001 that were updated...) and any 200 as long as the rear tires are the same diameter.  LOW gear ( low & high side) will be slower on a 200, but the other gears are the same.  Any straight 190 before s/n 9001 will be geared differently. Don't know the weight difference. Maybe 50 lbs ?