As a previous owner of a 145 (a 1969 that was only 10 years old at the time), I can only caution you in regards to the "Weakest Link of The Chain". That damnable Pressed Fiber Timing Gear.

However, now that the car you are talking about is 41 years old, I would be seriously looking at other engine components. For starters, the Cam Shaft for lobe wear. The lifters for related wear on their Flat Surfaces. In general the entire Valve train. Modern oils do not provide the appropriate lubrication for the flat tappet engine.

Next, Valve seat wear. this can be "casually inspected" with the head on by looking at the adjustment on the Lifters. If you have one (or more) that have the "stem" sticking up noticeably further than the others, you have a problem.

There are a thousand other things to worry about, but I'll stop with just asking you to pull the drain plug on the transmission to see if the fluid comes out clean or with lots and lots of sparkly little silver and gold bits.

Enjoy!