Just as an FYI for folks. The 70 incher was a little tight on our 69 K10 that we just finished. Of course you've got the transfer case added on there, but also the original Stewart Warner adapter made things very tight. We got it together, but it was under some strain. So we had one custom made. Very quick, high quality and reasonable price...here's the link in case anyone needs it...they're in Denver:
https://speedometercablesusa.com