All SBF head castings start with a letter. 6D18 and 6E19 sound like date codes. Cast on April 18th and May 19th during the 6th year of a decade. The casting ID will give the decade.
Fox body V8 head casting numbers are as follows.
1979 - 84 = C94E-6049-AA
1985 = E5AE-6049-CA
1986 = E6AE-6049-AA
1987 - 93 = E7TE-6049-AB
1994 - 95 = E7TE-6049-AB
1993 original GT40 castings = F3ZE-6049-AA
If none of these match,.. then the heads did not originally come from a Fox body Mustang.
The first 4 chars of the casting ID determine the year and origin of the head.
For example,
E7TE: E = 1980's, 7 = 1987, T = Truck, E = Engine.
F3ZE: F = 90's, 3 = 1993, Z = Mustang, E = Engine.
E7 does not necessarily mean it was cast in 87 or was specifically in a 87 Mustang. Only that its the 1987 casting. E7TE were in all 87 - 93 5.0 LX and GT Mustangs. E7TE could also be found in F150 trucks and Crown Vics as well. They were nothing more than corporate heads.
The block ID can be found above the oil pan behind the starter.
HO and non HO difference is primarily just the firing order. The cam will determine the firing order. A non HO roller 302 can be converted to HO firing order by swapping in an HO cam and rewiring the distributor accordingly. 302 HO has the same firing order as a 351. A none HO has a regular 302 firing order. I recently swapped in an E-303 HO cam into a 1986 Country Squire wagon for a friend of my father inlaw.
5.0 HO = 1-3-7-2-6-5-4-8
5.0 Non HO = 1-5-4-2-6-3-7-8
A9L is a MAF computer. Since 88 was a non MAF year,.. the EFI has been converted to MAF from Air density. A very simple 30 minute procedure. Does not mean much other than it was converted and the original ECU replaced with the A9L. A9L is one of the most popular ECU's. It has the latest 92/93 programming which made it more friendly for aftermarket bolts ons, cams and headers as well as working well with larger heads. Most tuners prefer the A9L over any other ECU. A9L was for manuals and the automatic equivalent was the A3M which can be substituted for an A9L in a 5 speed car. Both have the same programming as far as tuning goes,.. the A3M has extra tuning for use with the AOD tranny.
Hurst