K frame swap
I did the same setup in my 71 Dart, the K-member will bolt right in!
Although the K-members differ from F to A body you can also use 360 or 318spool engine mounts from F-bodys (Valorie, Aspen) and the late 70's lebaron style cars (not sure what body platform the laberon are!) which will bolt your 360 to your K-member! I believe the SB engine mounts are the same with the early 80's Mirrada and Cordoba can also be used on the 73-76 a-body k-member!
also Small block B-body spool mounts can be used on your A-body k-member!
the 318 mount can be used on your 360, you will need to make spacers for one side, the ears cast onto the 340 & 360's block on one side are narrower then the 318's!
I have used all of these combo's above switching engines around in my younger high school days, I would transfer insurance and engines one day so I could drive my 72 Charger or 79 aspen the next until a second engine was bought! My dad thought I was nuts! I later drop the 360 into a 74 dart using the same mounts!
Just some options to help you find your mounts!