Antifreeze in the oil makes me think there is a crack somewhere from the overheating. Typical head gasket failures are oil in the coolant, and combustion in the coolant. Coolant in the oil makes me think crack, though I'm not saying a head gasket couldn't do it. Also isn't there also o-rings that seal coolant between the timing cover and block that can leak? I would pull the valve covers off and pressurize the cooling system. You can then peer down into the timing cover and visually check for coolant leaks into the crankcase.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff