slant w 518, Or??

If you can find one, MaMopar used an adapter to mate a smallblock 727 to the slant in pickup trucks and vans back in the '60s. Transdapt may have something you could use also. If all else fails you can always put a Gearvendors OD unit behind a slant tranny for not a lot more than the 518 swap would cost. Hope this helps.