198 numbers matching or 340 clone...... opinions?

Hi all, I have a 70 Duster, very, very base model with 198 3 on the tree. Last year I considered selling it, Alaskan_TA talked me off the ledge and convinced me not to just toss the slant. I do like driving it, it is fun and kinda unique as y’all know. Right now it seems in good order, I tuned it up and switched it to no ethanol fuel and it seems happy. As far as I can tell it is numbers matching other than it has a replacement radiator in it. I know the engine matches, I have yet to scrap all the gunk off the 3 speed to see, but can’t imagine that it’s not. Looking forward it is going to need work, so here is the question, when that day comes do I crush the value if I switch to the 340? Should I just overhaul the 198? If I keep the 198, it is because it will be a numbers matching car, so, how do I find parts for the 3 speed and the 3 on the tree as the need arises? Just looking for opinions, truth is it is running just fine right now so I’m just kinda bench building here. Part of my indecision is the 198, I find almost no info or thoughts about it other than the rods are nice in a 225 and hey it replaced the 170.
Gimme those thoughts!
Cheers
Tim