I have a 75 Dart /6. It has the spool motor mounts. Did Ma Mopar use the same K member for all the engines with spool mounts or will I need the V8 one?
No. They are not all the same. Someone from the older A-body group will have to help with this one. The front track was widened when the 273 came out. The /6 and V-8 I understand used the same K-member. From 67-72, there were three different ones used /6, LA, & B/RB (67-69). From 73 on, just one K-member, the spool mount. The spool mounts for the 273/318 and 340/360 are available from mass market sources. A Schumacher B/RB kit for your K-frame ought to take care of a big block.