Re: Old dog learns new trick...Welding!
The photos below should help clarify what I did. Not shown are the end pieces from a standard kit mounting plate. I found the kit plate to not be long enough for the predator engine so I used the end pieces and made up angle iron rails. The holes for the engine are slotted to allow for some lateral adjustment and the long slots on the sides which bolt to the end pieces allow some forward and backward adjustment. I should have taken pictures which also showed the end pieces. If it still isn't clear I can take a couple more pictures. Seems to work well enough and uses what I had.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...