Was there a M41 Walker Bulldog that was fitted with a 105mm gun, it had a 75mm gun?

Rusty,
Sorry, can't find any info on upgunning an M41 with a 105mm. Do know that the Brazilian version mounts a 90mm but all of the other foreign users seem to still use 76mm guns.
Could have been a one off attempt. You can try the Squadron In Action book and see if there is anything there.

i believe that osprey has a book on u.s. light tanks since '45 with a swiss or swede m41 w/ a105mm gun.

I have the squadron book on the M 41 that shows it with a 105. I found this article on a website ( forget which one). The M-41CG is an M-41 modified with the 105mm gun turret from the Cadillac Gage Stingray, and has a sophisticated fire control system. There is a more-powerful engine to cope with the increased weight. This was produced as a private venture as an upgrade for customers’ existing M-41s, and none actually made it into service. (It is a "what-if."). The turret front and sides have lugs for reactive armor. The M-41 is the same idea, but uses the turret from the Leopard 1A1. Dont know how true any of that is but it was the only thing that I could find. Hope this helps. Bryan