In order to use reproduction SBF engine mounts, you would have to change your engine frame stands to the 1968-70 small block, hard top style.
1967 owners with 289 engines have the same problem.
The good news is that the frame stands that came in your convertible, can be sold to guys with 390 or 428CJ.
It may not be that easy. If you change the frame stand that will change the height of the engine- trans. You could end up with exhaust clearance issue in the tunnel. The pipes may hit the convertible cross member plate.
I had this problem with a 69 XR7 convertible. When I swapped the original frame mounts for small block ones, it shifted the engine/transmission about 3/16 of an inch. To handle this, I had to adjust the shifter linkage. There were no other fitment or clearance issues
You need the hard top “ENGINE PEDESTAL / FRAME BRACKET” and then the available insulator(what most call the motor mount) will work. The pictures I posted earlier are showing the deference in the 2 types.
Hold on to your '67 or convertible engine stands (I did) for when the above event takes place.
I replaced the engine stands/isolator on my '67 w/'68 spec parts from WCCC. Thanks Don, the engine stands looked brand new after a bath in the parts washer & a soak in Evapo-rust: factory paint daubs & everything.