Opel Key Master
Installing Mazda Miata Seats into an Opel GT
By: Keith Lundholm
By: Keith Lundholm
With our factory seat facing 50 years of age, many Opel GT owners understand the frustration of having them sun baked and broken down. Aftermarket racing seats tend to be too wide and too tall to fit proportionally inside the GT cockpit. I have found that the 1990-2005 Mazda Miata seats are a great choice for the interior and have many features if you know what to look for. First off, they are plentiful. Mazda built a billion of these cars, and seats can be purchased for cheap in most cases. Many times these seats come out of a wrecked Miata that was babied its whole life. I like the 1990-97 style seats best, as they featured speakers in the headrests. If you search carefully, there are seats with a special option called the "Mazda Sensory Option". This option included not only the head rest speakers, but a back rest seat bass speaker. This allows the driver to feel the music, and it works amazingly!
This tutorial is going to make it simple to perform the conversion, as I have documented all of the measurements and tools needed. First we need a set of seats, so recently I purchased a set of black leather ones off eBay. The leather was really nice on these seats, but the purchase price was $600 shipping included. There are aftermarket seat covers available in all varieties and options, so you do not have to find a perfect set, if you are going to recover them. I've purchased seats from a wrecking yard for $200 a set. You will not need the seat tracks from the Miata, but will need the bolts. If the seats come to you all together, you will want to separate the backs from the bottoms.
We need some flatbar steel to build our supports for the Opel GT seat tracks to mount onto the Miata bases. 1-1/2 x 3/16 flatbar can be picked up in most cases at your local hardware store's project section. I bought two sections of four foot pieces. The end result will be four pieces at 15" each.
I make short work of cutting these up on an iron worker. I have set these measurements to be as accurate as possible, so the hole pattern was drawn out on a layout table. My results are right on, so if your measuring is replicated, the results should end without any hole enlargement to make fit. I use Dykem layout dye on the ends of the pieces and also the center. I begin by scribing a line .375 from the base on each end. I then scribe a line at .875 above the base of the layout table on each end. This will be the spacing of the holes for all 4 pieces. Then starting about a half of an inch from the end of the bar, I scribe another line to form a cross on the .375 marked line. These will be my outer holes to line up with the Miata.From that intersecting line, I raise the caliper up .8 of an inch, and scribe the line at the .875 measurement. From the point of the first intersection, we need to raise the caliper 12.937 to mark the other end. My caliper only goes 12" high, so I scribe a center line, flip the piece, and set my scribe to the center line. I then subtract the difference from where I am at, in relation to the 12.937. I then add .8 of an inch to scribe my 4th hole. I then center punch all the holes.
Important note: The driver side and passenger side have a different distance to seat bolts. So only two supports will be made at these measurements. The passenger plates are at 13.687 between centers, and the inner hole spacing is 1.175 from each hole. Refer to the drawing for all of this info.
The intersections will need to be center punched and then drilled. I used an iron worker to punch the outer holes, but a 3/8 drill will be used on the outer holes. The inner holes will be tapped to 8mmx1.25 thread, and a 17/64 drill bit will be close enough for you to start the tap.