88 KX 250 Frame, What engines fit

[Reefmonster]

Could someone clarify what year engines will fit in a 88 rolling chassis, looking at a couple of 90 engines wondering if they will fit?  Thanks.

[DoldGuy]

REEF,
If memory serves me correct, the 88 thru 91 bottom ends are the same & the main difference in the top end is the head stay mount on the 90 & 91 is on the front of the head (perimeter frame) & the 88 & 89 is on the rear (heads are interchangeable). Hope this helps.
DoldGuy