here is a brief history of Honda's time line, but they don't list the 1989 trx350D foreman ?..hmm. --->
Honda ATV Model History Timeline, 1970-Present - Heritage - Honda News .
1986 FourTrax 4X4 (TRX350)
Honda's first ATV with full-time four-wheel drive features a limited-slip front differential. This powerful workhorse is equipped with a tough 350cc four-stroke engine, a vibration-reducing counterbalancer and a fan-assisted oil cooler as standard equipment.
1987 FourTrax Foreman 4X4 (TRX350D)
One year after the successful launch of the FourTrax 4x4, the celebrated Foreman name is born. The 350cc Foreman 4x4 features front and rear racks, a high-output, 310-watt alternator and an 850-pound towing capacity.
They list the release years, so the 350 Fourtrax came out in 86
86 and 87 Fourtrax were the same (350A), then there was also the 87 Fourtrax Foreman (350D), which went through 89.
The electrical systems were the same on 86 and 87 350 Fourtrax, but the 87 350D Foreman had a different system, and then the 88 and 89 350D foreman yet another system, so when looking for components the 87 350D is the oddball.
I was told the "D" in the 350D stood for digital, as in the fuel gauge.