You can try to put it in from the top (before putting the tank on the stand) - that is assuming you have the usual open top stand. Even if you have to remove some bracing from the top, it is safer than removing the vertical supports. The top braces are there to keep the stand from bowing out and has less load, so is less critical to be put back perfectly. If you have to remove the vertical supports, you'd have to make sure to put them back with structural intergrity ... depending on how the stand was constructed, that might take a lot of work.
Or you can get a smaller sump .....
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.