With certain exceptions any '55 to current production SBC/Gen 1 265, 283, 302, 305, 307, 327, 350, 400 can about interchange most non displament spec parts. Depending on years like heads, you may require an intake with matching bolt pattern like with Vortec heads. Now the disclaimer is not all parts will interchange. The main thing is knowing what year you Monte is (guessing from seeing your mirrors it'll be an '85 or older) & if that is an original or period correct 305. Hate to say a full on yes it all will fit then find out the one engine had perimeter bolt pattern valve covers & the other uses center bolt covers for an example. Pay attention if the seller did make any changes cause of the interchanges between the years an older block could have newer heads ('72 block with '96 heads) which could prevent the use of the intake (again guessing it's an '85 you have.)
Now for making things stiffer, I'd suggest boxing the frame & use the GN/GNX rear seat braces. Even new body mounts can help.