I was thinking of like the Frankenmotor 1.9TDI heads on 1.6L IDI
They used a 1.9 IDI
head.. IN the mid 90's the lucky Canadian #&*'s got a 1.9 IDI also referred to by it's engine code AAZ.. So they did still indeed have prechambers.. BUT
the 1.9 AAZ has a larger volume prechamber than the 1.6 which is what caused the lower compression..
The reasoning behind the larger prechamber on the 1.9 AAZ was to keep the compression down around the normal 23:1 range.. (I forget what the exact ratio was on those) IF they had used the same chamber from the 1.6 coupled with the larger bore and stroke, the compression would be sky high.. Basically the same principal as stroking a gas engine.. A lot of stroker kits come with a dished piston, or a cylinder head volume suggestion so that you don't end up with crazy high compression..
At this point there are no 1.6 TDI pistons.. Emiata (aka Prothe) has claimed to be working on such a beast, but it hasn't happened yet.. Chances are as actual TDIs get older, they will get cheaper and make a TDI 1.6 not worth the time..
Your 83 is a mech lifter engine.. Other than the member Saurkraut on here, everyone has been running their AAZ with the hydro lifters.. Address the extra oil return port issue and you're golden.. Changing the head to mech lifters involves A LOT of custom work.. Probably not worth the time and money either..
Shaving the head will do nothing for compression.. The valves are flush with the gasket surface.. THe only chamber in the head is the precombustion chamber (or precup).. If you had some means of shrinking that without screwing with it's operation (swirl and stuff), you could raise the compression..
Thinner head gasket is a not a good idea.. Once again, valves are flush with the gasket surface, and piston to valve clearance is pretty tight to begin with... Measure the protrusion of the piston and go no thinner than what that spec says.. Pistons making friends with the valves at high rpms is not a good situation...
I've often wondered how some sort of air heater in the intake (such as used on the Cummins) in conjunction with the glow plugs would work in helping the issue... Possibly leave the intake air heater on as sort of an afterglow function to aid in warmup operation...
Speaking of Emiata, do a search on here for "prothe" to get a feel for the vendor... On the other side of the coin Smokey Eddy on here has been using one of his AAZ heads with no problems...
Whew, it's way past my bed time, let me know if I wasn't making sense on something here..