You have a chassis issue. It's not out of fuel. It's loading and unloading the rear tires.
i had this suspension setting from many years .. Caltracs, Dana 60,monoleaf ..i have onky swap the engibe from 496 to 572 .. same transmission same axle ... same tires only change Engine .. the only difference is the weight .. 572 weight is 80 lb more than 440 block .. i think ..you think this can cause unloading rear tires?
You gained 76 cubic inches and are probably making more power. You need to tune the chassis.
Get some video of the tires. Bet you it's beating the hell out of the tire.
Chassis have Dana 60 , caltracs , monoleaf , connecting frame , double adj qa1 shock , never problem in many years , hook very good 1.40 60 ft with 3900 lb
