Fender tag info
Cool score, Brambles. I also have a bone stock 70 340 Swinger. I'm currently restoring it. Some facts I've learned are:
Not all cars have the VIN stamped on the radiator core support. Mine doesn't.
Mine does have the VIN on the trunk edge under the seal on the passenger side.
The VIN is stamped on the block pan rail passenger side, (2 letters and the sequential 6 digit build number.)
The 6 digit build number should be stamped on the Tranny case(right side for a 727) and on the side of your 8 3/4 third member(741) on the right passenger side.
An excellent number decoder site is mymopar.com mrmopartech at that site can answer ANY QUESTION!
If I can help you in any way, let me know.