The stock, base tires/wheels on a 71 C20 were tubeless 8.75-16.5C(6PR) nylon tires on 16.5x6.0" white steel wheels with painted hub caps. Much like the picture here. However it is very likely that your truck had larger tires at some point as most campers did. Most often it was the rear only that would have larger 10-16.5 or 12-16.5 tires. At the time these were a semi-low profile tire and not like the high aspect ratio of today's "off road" tires. The White 71 Cheyenne Super is a reasonable example.
If you want a steel spoke wheel like the classic Jackman Duplex they work, but present a very dated (cheap?) look to many people. In the typical White with pinstripes they will look the period part. My favorite of this
style were the 6 spoke.
That said my personal favorite are slots. In fact there is a thread you need to check out too.
http://67-72chevytrucks.com/vboard/s...d.php?t=372115
If I ever find an affordable 4000lb+ rated, forged billet 16" period style slot I'll be happy.
Biggest problem is 16.5 wheels need 16.5 tires. They are expensive and limited availability. But they are out there including 12-16.5 camper tires.
If you are driving it 16" or 17" make more sense. There are a number of threads detailing the use of easy to find Ford 16" steel wheels allowing the use of available radials and stock Chevy hubcaps. Forgive me for not providing one of my everpresent links!