Ok, so, 1971 V8 K member into a 1973 car with a 360?
It will fit just fine, but it has the biscuit style mounts instead of the spool mounts.
If you have a front sway bar for the '73, it won't fit with the '71 K. You'd have to get a '67-72 sway bar and move the tabs on the '73 up lower control arms, as the tabs were in a different place for the '67-72 sway bar. If your '73 doesn't have a sway bar then there's no issue, just remember if you ever buy one to get the '67-'72 type and not a '73 up style.
360's have a slightly different engine mount on the driver's side. You can either use some spacers to make a 318 mount work or try to find an original 360 mount. But if you buy a 360 mount, you'll probably find its the same as the 318 mount, as the parts manufacturers seem to only make the 318 type now. There's a couple threads running around on this if you do a search.