Help on K member
Basically any year 67-76 V-8 K-frame will work...The 67 has its own pain in the *** idler arm that is super expensive, so scratch the '67 k-frame...this leaves you with the '68-72 v-8 k-frame, which all have the same biscuit style engine mounts...the 73-76 v-8 k-member will work but they changed to the better/stronger spool type engine mounts, which you would have to buy in addition to the k-member.
Or since you already have a 67-72 type slant 6 k-member, you can get a v-8 swap engine mount kit from summit which is 60 bucks...
http://www.summitracing.com/parts/TRD-4695/
or the more expensive engine mount swap kit from schumaker...
http://engine-swaps.com/