1970 gmc 1 ton dually wheels

[playinsafe44]

my dad just got a sweet deal on a couple of trucks. a '73 mustard yellow 1/2 ton (250 I6, original with 60,xxx miles), and a '70 gmc 1 ton dually, flatbed with a 350, granny 4 spd, and nice flatbed. he bought them both for 500 bucks. we drove them away, the 73 is cleaning up real nice, but the 70 will need a little more tlc. right now we are looking to get some better wheels for it. the ones on it have some pretty serious rust. what are our options? i thought the eagle alloys 16 inchers would work, but them i was told that i cant run them on the inside rear, and then les schwab told my dad that he would need wheels custom made. so any suggestions would be great for wheels