I cant speak from experience but i might add a few things because they came up in a related issue i inquired about a while back.
I have talked to many people since i got into this hobby who seem to use their garage as a "tank room". To help with the cool nights you could add insulation to the tank - at least the back and sides. Most home improvement stores (HD, Lowes etc) sell styrofoam, polystyrene (or something like that). It comes in sheets - various thicknesses and some stores have different colours (Lowes has it in blue) if thats important to you. (i got some to insulate a tank but its pink - not everyones taste - so they paint it)
Really easy to work with. If you go check on your tank every morning you could even add a removable sheet to the front you just place there overnight.
For a tank that size you'd probably use 2 heaters (or more?) anyways - so you could size them a big bigger (more than the usual 5wpg) and still be safe because even if one gets stuck in the on position it wont be able to cook your tank.
Those are my $0.02 input - hope they might've been of some help.