if I want to build a Chinese type 59, should I get a trumpy kit (which i've heard isn't great) or work with a tamiya T-55.

If the T-55, is there somewhere that will tell me what I need to do for the conversion?

Thanks,
John

The Trumpeter kits are a bit too deep in the lower hull (to accommodate an electric motor), and the tracks are less than impressive. Detial is soft by modern standards. Early boxings were molded in ABS rather than polystyrene, which had to be glued with Plastruct or other ABS cement, though those are probably off the market by now.
On the other hand, the T-59 is basically an upgraded T-54, which means lots of changes to the turret and engine deck if you want to modify a Tamiya T-55. Later Chinese variants had detail changes, like treadplate instead of welded rod headlight guards, and laser rangefinders. You can look for resin conversions, or just kitbash the Tamiya and Trumpeter kits together.