This is what I'd probably do.
I would not heat it.
I would weld another pipe/rod/whatever across the end to make a Tee. This will be used to turn the pipe so that the bend faces up or down, but cannot turn as we press on it with whatever.... It stabilises the pipe orientation.
Once thats done, If I had a decent tree available (and you do), I'd chainsaw out a slot that would take the end of the pipe and the cross piece. This will allow accurate setup of the pipe orientation. It can be blocked up either end of the T within the tree slot to make it so that the pipe cannot rotate, but instead will remain faithfully in the orientation we place it.
Then, if you place the pipe in the slot, with the bend downwards,.... park the truck above the other end, bottle jack in the middle, and pump it to true... repeat until it remains true.
If you over doo it, then simply rotate the pipe 180 degrees and do it again.
It will need a length of timber between the jack and the pipe to spread the force.
This will work, and with the most basic of things, you have full control of bend and angles. Just need a decent tree to give the stability. If you have tractors as well then it's lots easier, may not need the tree.
...............oztules