yup usually the full 25mhz 040's run fine at 33mhz... however, you will notice it will get quite warm, so you should get a 486 heatsink on there, or something to heat sink some of the heat away from the cpu,   I'v ran lc475's with full 25mhz 040's @33mhz, many times  but there is a fan right there next to the cpu, and i am sure that does help.   With a 575 in a CC or even a 575 in a 575,   you might want a heatsink.  with your IR temp gun you will see temps between F 128 and F 145 depending on what you are doing,,, witch are considered safe temps more then likely.  Just with all this stuff being vintage and all, might make it last longer... ?