had right pig of a day today removing the diff out of my STM only to try fit my new 7" 3.6 and as u guessed even though I was told would be straight fit I need spacers anyone know where I can get them from płease and sizes I will need

The 7 ½" uses individual bolts
7" uses a through bolt
So you may need a long bolt then simple washers will suffice
Or a tube cut to length

Also best check your drive shafts, 7 inch use 100mm lobros, most 7.5inch diffs have 108mm lobros.

Lobros you mean the end plates that connect to the drive shafts?

Yeah

Is the 108 the total plate diameter? Or distance between holes

Distance between holes IIRC

are you sure as measured and it appears the plate is 100mm

Craig. Spend the morning reading this.it should help a lot
http://www.super7thheaven.co.uk/components/sierra_rear_differential/

You are measuring the plate.

100mm lobro has hole pcd of about 84mm from memory.

http://www.gwr-fasteners.co.uk/m10-x-20mm-od-spacers---standoff-collar---stainless-steel-21282-p.asp

so have you landed lucky and got the correct 100mm lobros to fit onto a 7 inch diff?

Something like the above will do for spacers if your worried about using washers.