'70 c10 "whining" noise questions

[Stumpf22]

Hey all, I'm new to this site and have been doing lots of reading and searching and this site is awesome! Lots of information! I just picked up my '70 c10 last fall and keep putting little by little to get it more road worthy. I do buzz up and Down the back roads from time to time and when I do I have noticed a "whining" noise that sounds as if it's coming from the trans area. The noise gets louder the faster I go. When I push the clutch in and rev it, there is no noise. And also if I'm cruising and let completely off the gas so there is no load on the trans the noise goes away. Any one else have this? Is that how these trucks are? Could it be the clutch making the noise? The trans fluid level is good.

1970 c10
2wd long box
Small block v8 was told its a 350 but haven't decoded the numbers yet
3 speed column shift

Like I said if been doing a lot of reading and searching and the amount of info iv gathered from this site has been so helpfull and want to say thanks in advance. I'll try to figure out how to post some pics.