Below is simply a brief explanation as to the differences twixt the "Rallye" and "GT" guage sets that were available as an option or accessory on 1972 and earlier Volvo 140 series cars.
 
 

In the above picture, you see the fronts of each set. That would be the "GT" gauge cluster at the top, and the "Rallye" cluster below. Of course,  the most obvious difference is the lack of an oil pressure gauge in the "GT" cluster. And the seemingly random placement of dummy lights on the rallye set. More details to follow...
 

Here we see the middles of the two sets. The rallye cluster on the left, GT on the right. Again of course, we see the oil pressure guage on the rallye cluster, as well as the different light layout. Also, the fuel and temp guages are more towards the center in the GT set. But also notice the difference in the gauges themselves.  Machined aluminum pivot covers are visable on the rallye set, the pivots are covered on the GT set. The green and red markings are also different.
 
 

Sorry about the lousy pictures on this one. Here are the two tachometers. They are the same size, and the only difference seemst to be the printing. Note the higher redline on the rallye tach (left again), and the fact that it says "rallye" on the bottom. Otherwise, they look about the same.
 

And here we have the speedometers...again, they look about the same. Except for minor differences in the printing, inlcuding again, the "rallye" label on the one on the left. Also note (and jeez...I only notice this myself as I type...) the numbers on the inside of the marker lines on the rallye guage, whereas the numbers are to the outside on the other.  And its the same on the tachs, of course. Can't believe I never noticed that detail before.....
 

Now, all that said, I rather like the rallye cluster more. Looks a little more serious and has the oil pressure gauge that is lacking in the GT cluster. Until you look at the backs of the two sets....

Here at the top you see the spaghetti mess of wires of the rallye gauge cluster.  Below is the clean look of the GT set. For this reason, I expect the GT set is A) a newer design, and B) a much more reliable, usable system. And in the case of mine, it ain't broke in the back like the rallye set is....but I'm gonna fix 'em both someday, and I plan to use the rallye set in whatever car becomes my hotrod Volvo someday.....
 

Matt B
'71 145s
'72 164e
65 1800s
and other non-Volvo sillyness