According to one of Fords websites :
For a 1988 LTD Crown Victoria , 351 cubic inch / 5.8 litre V8 engine :
( the spark plugs are gapped at .044 inch )
( .044 inch ) according to fordparts.com
( .044 inch ) 351 Windsor and 351 Modified for 1978 Ford truck
The 1976 351 Ford engine spark plug gap is .034. Most spark plugs will come pre-gapped from the spark plug manufacturer.
.044 inch
0.044
.044 inch
ford 351 windsor
.044 inch
.044 inch for 351 M and 351 W
.044 inch
www . motorcraft . com ( no spaces ) shows : The spark plug gap for a 1994 F-150 - 351 V8 ( 5.8 L ) as .044 inch
.044 inch