Alright, we have all of the GM opinions, now for the Ford opinion. Head gasket eating machine. Carry a spare pair with headbolts when driving. Gas mileage in a 3800lb car, I seem to remember being somewhere in the mid 20'* highway(no better than my 4.6, which is far more than a "wothwhile" development, especially when coupled with the 4R70W ).
3800 is far superior in terms of reliability, but not flawless with the LIM gasket failures on all versions, and the UIM failures on the L36'*. Vast amounts more power, when compared year to year with a Ford 3.8L in the mid-late 90'*.
Ford DID use the 3.8L SC in the Cougar, but it didn't sell so they pulled it. That was in 1989 and 1990.
Also, a Ford 3.8L aftermarket exists. Otherwise, the SC guys would have a helluva time getting their Ford 3.8L powered Thunderbirds into the 10'*.
is just one of the few places I know of that actually caters to the 3.8L crowd. Another website I can't locate was a very popular one a while back.
However, SCCOA.com and 3.8mustang.com are forums regarding the Ford 3.8L and performance applications. Yes, they do exist.
is another place to buy parts, though poorly laid out...
I guess, in the end, the 3800 is a far better engine, but the 3.8 from Ford can be made to go just as fast, even though it'* far less powerful and reliable out of the box.
Additionally, the mid 90'* engines did NOT have knock sensors. If you ran lean, you pinged. The SC guys strongly recommend an oversized exhaust system and headers before you consider dropping pulley sizes. However, they claim that doing these things also gains you a considerable amount of power(I can not verify this claim). Something to the tune of 50hp from headers and exhaust(replacing the resonator with a high flow one that is).
supercoupeperformance.com carries a small supply of N/A 3.8 upgrades and a plethora of upgrades for the */ced 3.8'*.