Need Help with my old Savage Single Shot!

Hello Everyone. First time poster - long time shooter! I have an old Savage rifle which started life out as a 22-250 some time back. I bought this rifle at a gun show about 15 years ago for $175.00 and it was old even then. The original barrel was a 22-250 and had many - many rounds through it, even by myself prairie dog shooting in Montana. I was surprised that it still shot MOA. It is a single shot varmint style rifle with a very nice walnut stock , hand checkered, with a nice palm swell on the pistol grip. It's serial number is B909179. I haven't been able to find any information about the "B" type serial numbers. I do know that much of the information was on the original barrel. Since then it has been replaced with Shilen SS barrel chambered in a 6mm BR. It just flat out shoots; easily shoots .25MOA. Would like to find out what model it is? Is it a rarity? Should I have kept it in its original condition? :frusty:THANKS in advance. The reason for asking, I want to replace the trigger with a Basix because the trigger on it right now is pretty lousy.

It's a 1975 model 112-V, actually the first year it was offered.