Questions from Norway

[NorwayC-10]

Hello
New member from Norway here, with (of course) a lot of questions.
About a year ago, I got my hands on a –71 C-10 stepside. It was imported from Arizona to Norway about 3 years ago. I have done a little work on it during the wintertime, but there is still a lot of work left to get it the way I want it. I have been looking around on this great site for a few days now, and I have found answers to many of my questions, but there is still a few things I am curious about.

First of all, my transmission. The truck has a 4-speed manual and according to the original “owners and drivers manual” this is called CH465. Is this any good or should I try to get it replaced? I don’t think I have seen this transmission mentioned anywhere here.
If I’m keeping this transmission, would it have any significant influence on the rpm to change the rear axle gear? As far as I can see, it is an all original drivetrain and everything works just fine.

During the winter, I have dropped it 2/4. Drop spindles front, coils and shocks rear. Will it be any problems to put 20x8 rims front and 20x9,5 rims rear? I have disks in front and drums rear.

The left rear fender has a “space” for a spare tire. Is there a replacement panel available for this, or do I have to buy the whole fender? Shipping from US to Norway costs a lot of money and used parts for his truck is almost impossible to come by here.

Maybe the answers to these questions already have been posted here, but I would be grateful for anyone who would take the time to reply. Thank you