Don't recall seeing them on their site, but maybe I need to look harder. It's more rewarding to scratch build it anyway.
This thread has inspired me to tackle this project of yours for myself. Truth be told, I've been kicking it around for about ten years anyway. I happened to have a '60 Chev kit and two '64 kits in my stock that I had for my unfinished '60-'66 line project and have begun hacking away. I'll be a regular visitor to your site for a little while, hope you don't mind.
I may even scratch build the engine if I can't adequately kit bash one. Looking at that other link you provided, none of the blocks I have in my parts box are quite right. I may mold it up if I do scratch build it, so in that event, I could part with a casting if you wanted one.
There was a '62-'66 GMC version of the Caryall Suburban, '64 IIR, that someone had converted in a car model magazine show special a few years ago. Nice model.
What are you planning to do for the tranny on your model?