I recently traded into a 336 in 30-30, which is my first foray into centerfire lever guns. My first firearm I purchased with my own money was a 39a on my 18th birthday and marlins have always held a close place in my heart, but Somehow I haven’t owned one of these until now. It has some mild rust on the metal and wood has some dings. I plan on refinishing the wood with tung oil and cleaning up the internals but no rebluing. My question is the internals are very roughly machined with some rust on them, but how far is too far in polishing them? I don’t want to end up with a lot of slop due to excessive metal removal. Thanks!

First I would get the rust off and if it functioned smoothly I would leave well enough alone. A light polish won't remove much metal if you feel it is necessary.

My 30-30 is a '75 Marlin Texan. Kilt lots of deers and quite a few piggys with that rifle.

Those mid 70s models are great guns. I have 2 of them and they are my favorites. Just take it apart and spray everything with oil and rub them down with steel wool. If a part is real rough I use 400 thru 1000 grit wet/dry sand paper to smooth things out. I just did it tonight on a project gun. It is hard to remove too much just sanding by hand unless you do it every day for a week! You will know when to stop.....when it's shiny. Just hit it with cold blue afterwards if it was blue to begin with. I also like these. They seem to go a step farther on stubborn spots on blued parts
https://www.americanrifleman.org/articles/2018/1/24/product-preview-big-45-frontier-metal-cleaner/

I use a 6" buffing pad & blue polishing compound

Buff the pivot points....hammer/carrier screw......lever cam...

Hammer nose & pivot point...ejector.....ejector groove in bolt

Left side of bolt around around the above groove

Changing main spring to lighter Wolfe will help...may get light primer strikes...test !!

http://marauder.homestead.com/files/TUNING_M_1894.htm

Thank you for all the replies. I have all of the metal pretty well cleaned up, and the wood is stripped and on coat 2 of tung oil. I can’t wait to shoot this thing once it’s all together.