Fluid level rising in the trans is a sign of the radiator leaking antifreeze into the transmission cooler. A glycol test will verify.

You may get by with a new radiator and a transmission flush, but don't bank on it. Worst case scenario... glycol can contaminate the frictions and water can rust and seize pistons and valves.

I'd swap the rad and flush it, then see how shifts. Monitoring adaptation if possible will provide insight on how much damage is done. Barring that the seat of the pants will let you know.

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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