What year 5.0's have the valve covers without any ribs inside?

[Rhombeus50]

5.0 valve covers without the ribs. Was this only for the '93 years?

 

[lager94GT]

I bought some from ebay stamped with a 92 with no ribs.

 

[cevtv]

I think it was mid '91 and later.

 

[maverick0716]

What do you mean ribs on the inside? Because the earlier year valve covers had ribs on the outside. Do you need them to clear for 1.7 rockers or something? Because the thing that hits those are the oil baffles.