[57taskforce]

The front if original will be a 44. I've seen Some of the K/20 chevys have the 60 rear as well but it's not very common. Most K/20 chevys got the ho52 rear. Ive only seen gmc get the 60 rear. Your truck is definitely a mut, however as said above if it's registered and your not worried about originality than no harm no foul. That tool box bedside is relatively uncommon and altogether rare if it doesn't have any rust. My door is perfect but under the door on mine is rusted out. You've got what looks like a solid start. Much better than most. The hole in the drivers bed side is intended for an auxiliary tank, not to replace the factory tank in the cab. Obviously it sounds like it's long gone

Edit: Jim types faster than me!