13.20 mph

451Cuda is right, Gremlins never came with a 360. The biggest factory motor was the anemic 304.

If you know the year of the motor, here is a rough indication of stock horsepower:
1970-71 was 285-295 HP
1971-75 was 175-220 HP
1976 was 140-180 HP
later 360's were in the 160HP range, stock.

From Wiki:
This engine was used in the 1970 AMX as the base engine and also in the 1970 Rebel, 1971-1978 Matador, Jeep J-series trucks 1970-1987, Wagoneer (SJ) models from 1972 to 1984, Cherokee (SJ) from 1974 to 1983, as well as in the full-sized Grand Wagoneer from 1984 to 1991 - becoming the last carbureted engine used in an American-built vehicle. The 360 V8 was also installed in the Bricklin SV-1 sports car for 1974 model year.

The 360 was the last AMC V8 to be manufactured. It continued to be produced after Chrysler bought American Motors in 1987 as the standard engine in the Jeep Grand Wagoneer through 1991, with the only modification being the "360" casting replaced with "5.9L" on the side of the block.