Hallo Reinhold,
zum Thema „Umbau auf Schaltgetriebe“ gibt es auf den US-Sites diverse Beiträge. Ich persönlich halte einen solchen Umbau für viel zu aufwändig und kostspielig. (Abgesehen davon bevorzuge ich ohnehin das Automatikgetriebe). Es bleibt aber natürlich Sache der subjektiven Einschätzung.
Hier ein Auszug aus den o. g. Threads, hoffe, sie sind hilfreich.
Auto 
Manual Transmission Swap
Recently completed an auto-to-manual swap on my 85. Most difficult part was cutting the
firewall and adding the master cylinder mount. Everything else was just bolt-in. I got all the
parts from Mark at 928 Int'l (714-632-9288). He supplied me a close-ratio, limited slip trans with 2.75 final drive ratio, freshly rebuilt, as well as all the associated bit and pieces. They were very helpful and supportive, and the job went very smoothly. This completely changed the characterof the car, waking up the performance and feel of driving it. It knocked nearly a full second off the 0-60 time, even with me babying the launch. I would highly recommend the swap, if you are attached to your particular car, as I am. Cost will depend on how many new parts versus used parts, model year, etc.. You will have to talk to Mark about that. My conversion cost me about $3,000 doing a lot of the work myself. It could cost quite a bit more if you have it done at a shop.
*Steve
I thought I'd pass on some info on this conversion. I do not normally recomend it as it is
usually cheaper to sell your AT car and buy a 5sp but sometimes there are other reason in this decision. We have helped 5 people do this conversion and all were very happy they did it.
Most were done by the owners themselves and it was not terribly difficult but it is a little time
consuming. The cost will very depending on the parts used. You can spend as little as $750 for a used 1979 transmission or more than $2,500 for something rebuilt like a 1989 GT with LSD.
You will also need to change the following;
flywheel
bell housing (on some years)
torque tube
rear cross member
brake pedal
shift lever and trim
You will need to add the following:
clutch kit
intermediate plate
short shaft
guide tube
pilot bearing
clutch arm
pivot bushing
clutch slave
clutch master
clutch lines
shift coupler
forward ball socket
shift rods
You will also need to modify your firewall to install the clutch master.
As you can see from the long list of parts it can get expensive. Having done this 5 times now
we have a pretty good handle on doing this. Would I do it on my own car? Probably not but I
have been tempted to do so when I've come across a very nice AT car.
Mark Anderson
928 International
Grüsse 
928robi
