I bought an ex u haul truck. With only 188,00 miles. 7.3 with 5 speed with super low 1st gear. I think the trans is a clark or spicer. Truck looks like its only a couple years old under the hood or underneath.Motor even looks new,maybe it was a replacement? Got it from a church. It has a 26 foot box and is the low profile version with air bags in the rear. I think it has the 4.33 rear gears as the truck will run 65 on interstate. I am going to use the truck as a toy hauler (only motorcycles). But the trips I will take are anywhere from 5-10 hours. I really need to be able to do 75 on the interstate. I know the truck has a SAE 2 bell housing. Can someone please help me figure out a 6,7,10 speed transmission to help with my top speed? I plan on adding a turbo kit from hypermax. But before I drop $3k I want to try a trans swap first. Thanks in advance.