IMHO, I reckon,, 1971 round case X5 MC250
71 engine because the X5 250 went on to receive sandcast outer cases for 1972
That style of 250cylinder head didn't appear till the 1971 X5
The swing arm has a narrow space between the pivot tube and brace tube = converted Square/barrel arm.
Frame has narrow seat subframe = first appearance X5,
Round clutch cover needs "through frame" outer cable anchor underneath in frame cradle = still a squarie frame=X5
That is one hell of a rough LTR conversion = X5 frame converted.
So a rough LTR conversion to a 1971 X5 close ratio MC250 with a sprinkling of some
rarer 125 goodies
As for as fiberglass tanks go,,it has a desirable smaller 125 tank
it also has small diameter symmetrical 125 front hub, but it is the wide one which does not crack like the narrow one does= desirable,,,,,