I upgraded my 3640/25 with a 060/50 processor. Simple upgrade and booted right away.. However, it froze a lot at first and I was finally able to install mmulib and it seems stable.
I got my plipbox running and loaded IBrowse and it worked much better, but since I lost my VA2000, I'm running overscanned 640x480 (700 something by 500 something iirc) through a 8220. It "works" but amiga.org didn't look that great... the site is too wide. I switched to mobile view of the site and it helps, but I think I really need a higher resolution but I think I'm at the limits of ECS.