I have a 74 duster and it has a /6 in it i am changing it over to a 318 anyone know a cheap way of doing this or do i have to go with Schumacher mounts?

Schumacher mounts are cheaper than changing out the K-member.

IIRC,the conversion mounts are the way to go.

if it was 72 or earlier,you could use a truck motor mount on the pass side and a 72 or earlier car mount on the driver side to bolt a 318 right into the /6 k frame.

if you change the K frame stay with 73 up v-8 k-frame on the 74 dart IMHO

How are your welding skills?
I have converted 6 slanty k members to V8 style with some metal stock and a MIG welder. Cost? about $20 for metal and grinder discs. You DO need a stock V8 k member around to use as a pattern though.....
A used 73-76 V8 k member can be bought for less than the conversion mounts. I've sold some at swap meets for between $85-$125.