Listing of k frames for 1970-71 with the applications.
Generally, V-8 k frames are the same with some differences (skid plates for the HP engines) Motor mounts are different w small block and big block engines
Here's the 19701 K-Frame numbers:
10 #2962010 Crossmember (K-Frame) 225 Engine
12 #2962012 Crossmember (K-Frame) 318, 340 & 383 Engines
14 #2962014 Crossmember (K-Frame) 426 Hemi w/ Skid
52 #3583052 Crossmember (K-Frame) 318, 340, 340 T/A & AAR, & 383 Engines
70 #3583070 Crossmember (K-Frame) 198 & 225 Engines
74 #3583074 Crossmember (K-Frame) 318, 340, 383 & (440 w/ Skid) Engines
76 #3583076 Crossmember (K-Frame) 426 Hemi w/ Skid
77 #3466477 Crossmember (K-Frame) 318, 383 & 440 (440 w/ Skid) Engines