Hi guys, i want to put a 4 speed tranny on my 96 because it sucks to have only 3 and i get very bad gas mileage as well. i know that having a 5.9 under the hood isn't a gas saver but if had a 4 speed the truck will feel lighter and the rpms won't be as high always. Now, take in count my truck is not a mpfi , it has the older TBi system. what year should i be looking for in the junkyards to make a plug and play swap? do i need to change the differential also? thanks in advance for the info.