Tech Inspector,
I would call Chevrolet Customer Assistance Center back at 800-222-1020 and request a free 1971 C/K “Resto-Pack”, as the phone jockeys that answer the calls are not technically trained and are just contract employees that swing through a constant revolving door. There is no way they could take a stab at answering that question over the phone.
The Resto-Packs are a thousand time over photo copy concoction of brochures, order guides, tech info, etc. It should have something in there about engine availability in each truck model. K10734 (short bed) and K10934 (long bed) are the model codes for ½ ton 4x4’s. I have a 1968 Resto Pack in front of me and it say’s 327 was the largest engine available in the 1968 K10 and K20. I know for a fact the largest you could get in a 1971 K10 or K20 was a 170 Net HP 350 but if you need supporting documentation, the CCAC Resto-Pack will be pretty much be your only option unless you find a Chevrolet dealer with a 36 year old order guide. Unfortunately, I cannot find the other Resto-Packs years I have stashed around here somewhere.
The quality of info in each Resto-Packs vary depending on who put them to gether at the time so you might want to order a 1970 – 1972 guides. If you order a 1998 and 1999 C/K truck Resto Pack you will get one that I made
when I worked at CCAC when it was still operated in-house by Chevrolet Motor Division. I also reworked many early 70’s El Camino and Truck Resto-Packs but I cannot remember if 1971 was one of them.
BTW….Big blocks were first available in K20’s (4x4) in late 1978. But, Suburban did not receive a big block in the ¾ ton 4x4’s until 1992 when the new GMT400 platform was introduced. Hard to believe but it is true!