That's pretty much it.
Usually, if there's a number on the part, it's an engineering number. You'll never find a part number directly (stamped or molded) on a part - only on a sticker, but even a sticker number may be an engineering number. Then there are manufacturer (vendor) mold numbers, etc...
It's sooo much fun.
Ford Parts Monkey since 1985
1981 F100 Flareside - Black, 302-4V Roller/AOD
1986 F150 Flareside - Medium Fire Red 302/AOD
1989 F150 Standard Cab 4x4 - Dk Shadow Blue 302/AOD
1993 F350 4x4 Crew Cab - 7.3 IDI/ZF-5
I think it's a sickness...