Here's a 50-52 harness, ask if they offer the earlier harness.

https://brillman.com/wire-harnesses/?fwp_product_vehicle_compatibility=vehicles-chevrolet-truck

This shop is close to me.
They're making a somewhat modified one for my 51 GMC. They do really nice work and use the best materials as far as I can tell, I've visited a few times.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-