Thorens TP-16 Tonearm cartridge mounting issue

Recently, I have acquired a Thorens TD-160 MKI equipped with the original TP-16 tonearm and headshell. I am using Dynavector 10x5 and Grado Gold cartridges but would like to try a Reference Grado in the near future. The problem lies within the headshell of the TP-16 tonearm, as it only allows for mounting from underneath the headshell and there are no holes on the top. After close examination, it seems I can remove the lid of the headshell but there remains a top that lies just above the threaded cartridge plate. Ideally, I would like to have 2 slots located above the headshell plate for cartridge installation and adjustment, this would make installation for Grado Reference and other cartridges much easier.

Does anyone know if there are other headshells that I could fit directly on the end of a TP16 with open slots on the top? Maybe a MKII headshell would work but I am really not sure?

Here is a link to a picture of a TP16 tonearm-

Thanks to everyone for your input.

Just a note - it seems there is no headshell on the Thorens TP16 MKII, just interchangeable arm wands.
How about screwing through the cartridge body and into the tp16 tonearm sled with a longer Thorens screw..You can get the longer screws and maybe go right through the cartridge body and into the Thorens headshell sliding sled...Instead of screwing from the top,Screw in from the bottom up.....?
You wouldn't be using the screws with the Grado wood body but longer Thorens screws.......
The TP-16 was revised at least two times that I know of. Each version had a different "headshell" design. I think one version actually had a removable headshell with a bayonet-style mount, and another had the removable armwand and a more traditional-looking headshell but it still required an unusual cartridge mounting technique as there were still no slots at the top. Why Thorens designed them this way, I have no idea.

I believe the last few years of the TD160 used the TP90 tonearm, which has what you're looking for. Perhaps the armwand is interchangeable with your TP16. The problem is, Thorens parts are rare and expensive and so this might be out of your comfort level in terms of experimentation.

The easiest solution in my opinion would be to swap out the arm completely for a Rega or Jelco or something in the $300-$400 range. I've also heard that the Linn Basik Plus and Akito work pretty well on Thorens decks. And, of course, if you came across a trashed parts unit with a TP90 arm, I don't see any reason why you couldn't swap arms.
Thorman, that's a good idea going from the bottom up but the factory holes on the Grado do not go all the way through the body. Grado may, however, drill out a cartridge body for me if I inquired about it.
Ekobesky, I originally considered swapping out the TP-16 in favor of a modern arm but I feel at this point the Thorens arm is nice enough to keep. I have rewired it completely with Cardas tonearm wire, re lubed and re adjusted the bearings, calibrated the arm and it sounds great. The entire TD160 has been refurbished and properly setup and has proved well worth the effort as it is a whole different sounding table at this point. Internally, they unit has been dampened with cork liner, new Thorens belt, cleaned and adjusted springs, addition of gold rca jacks and a removable IEC with Cardas silver solder used throughout. If you guys want to see the finished 160, take a peek on the system page of my account, there is a picture of the table there.
What the other posters have not mentioned is that also if your arm is the TP-16 Mk 1 version at 16.5gms effective mass,you probably have a mismatch using a Grado Silver on that arm.The Grado weighs 5.5 gms and the compliance is high at 20cus.This would result in a tonearm,cartridge resonance of about 7.4Hz which is actually quite low i.e too near the resonance of the table.You would want to be around 11-12Hz optimally.You can get a lot of info with a seach here on this site about addressing this issue.A cartridge with a lower compliance than a Grado would be a way to go.
Stefanl, compliance is something I have only glanced at, the general information I have about the TP-16 MKI is it is a medium mass tonearm and the Grado should work. Is there a site, link or calculation you could recommend for determining proper cartridge/tonearm compliance?
Found a formula for calculating compliance here -

This really helps!
The cheaper Benz Micro cartridges,Benz Micro MC20E2-H MC20E2 High Output Moving Coil or the Benz Micro MC20E2-L MC20E2 Low Output Moving Coil cartridge seem to be a good match for your Thorens arm at around 10.9Hz,if you need a suggestion.Both are available from LP Gear.
Does anyone by chance know if the TD166 motor is the same motor that is used in the TD160 MKI? I am searching for a spare and found one from a TD166 but am not sure if this is the same 16 pole asynchronous motor as used in the 160.
Chris74 ; Check with they have a Thorens dept and are usually available for technical questions pertaining to Thorens Vintage...You also could check with he does upgrade and custom work to Vintage Thorens tables