this allstate would equate to a VA5T/ 788.104 (its an old widebody handlebar bike, right? with the glovebox under the seat?) Anyway, this is a piston ported engine, through a bolt on manifold. The 125 version of that engine is called a VN1T and the 150 version is a VL1T. So if the headbolts are in the same pattern (which they almost always are) then the head & jug will bolt on. If the manifold bolts are the same then you could maybe get away with your stock carb/manifold. If not then you also need the carb/manifold from one of these VL1’s and that is a Dell’Orto MA19. The VN1 has a TA18C. But then you also have a wrist pin and smallend bearing to worry about and different compression ratios and gearing, but these aren’t excessively different so it should be ok. The VBB is definitely a no (completely different type of induction), the VL1T head exchange, i would say maybe…. your best bet is to try to find a VL1 engine complete (which unfortunately will not be easy or cheap) and bolt it in there in place.