Ok know they can be used but do they work with relative ease?

All depends on the width and ET of the rim, 7's can be made to work on a narrowbody car. 8's wont fit without GT fenders or alot of rolling of the rear fenders.

So it will depend on what widths the 944 had 7's all around or a 7" front and 8" rear setup.

951 - 7" - same offset as 911 fuchs
951 - 8" - different offset from 911 fuchs. Desirable for 911 since it lets you run 8's on a narrow body car.

Here is a handy resource: http://www.944racing.de/wheelweights.php

The 15" Fuchs for 944 were the same as 911 Fuchs, even to the 911 part number. The 7" offset is 23.3mm and the 8" is 10.6.

The 16" Fuchs for the turbos are different, have a 951 part number. For those, both front and rear offsets are 23.3.

not with relative ease
usually at least fender rolling and potentially fender lip painting are necessary
I know Ron had 7inch wheels under his car, but had to use 185 width tires to do it

the 6x15 inch fuch is going to fit almost for certain
the 7x15 fuch is not guaranteed