do i have to adjust my dash after getting my 18's on?
i remember that there was a site that you could check if you needed to adjust the dash it would tell you by how much.

i have an exchaser so it will be easy

hope you guys can help me

I guess it depends on how pedantic you are

After I got my 17's I sat a stock rim with pizza cutter tyres next to them and there was sweet FA difference in diameters. On a recent speed trap check (don't know how accurate) my dash was reading 100 and I got checked at 96, I'm not too fussed with adjusting that to perfection as its on the safely inaccurate side of the dial for speed camera's.

To adjust the dash you either have to replace the speed sensor with an appropriately geared one or use an interceptor to alter the signal being generated by the sensor...

So I guess get those 18's on cause that's the most imprtant thing and see what happens after that...

i already have them on lol
http://www.fordmods.com/forums/viewtopic.php?t=12692

i have an exchaser dash that allows the speedo to be adjusted by +or- 0.5% and i remember a website that compared the old rims with the new ones and then told you how much to adjust it by.....

i think its ok though but the only thing is that the revs are now lower and im hoping that it wont damage my engine at all

you mean this?
http://www.fordmods.com/forums/documents.php?doc=30

I have on the rear 18/8 with 265's on and I can swap between the stockers & the 18's without recalibrating the speedo so work out the diametre & a good profile and you'll be sweet