Congrats on the 74!
The 5.45 is a great round. If you don't already know...here you go Russian 5.45x39 53grn FMJ 1080rd Can
By the time it shows up at my place it becomes .13 a round. Cheaper than anything else I have except 22LR. Picked up four 74 mags last order, three were plum circle 21's and one Russian plum. It looked like someone had already stripped the paint on them too.
We all look forward to seeing what you do to yours.