Joe
I must be bored, or maybe it's b/c I missed the AACA national in VA due to Rain today...

but when I hear talk of a rare 66 SS, however remote the possibility of it still having the orig. drivetrain....well, I can't stop hoping it is saved.
The 66 SS Ragtop will have, as stated earlier...a starting VIN Number which is UNIVERSAL...138676 followed by letter designating the assembly plant it was born from... ( I won't list all seven) and then the remining numbers will be the car's sequence number off the assembly line...ie., 138676Z177205 might be what you would see on the VIN TAG attached to the door ( Z indicates Fremont, Calif. built) then b/c each plant's starting VIN was with 100,001., this example would be the 77,205th car built at the Fremont plant for the 66 production year...remember the production year didn't start in January either., and this would represent all cars being built at this plant, not just Chevelles.
That little background is to set you up for what you will look for on the engine...specifically the passenger side of the block deck as it extends forward past the right cylinder head. This will, though it may be painted over or covered in grease and grime now, be stamped with alphanumerical characters, manually stamped to show the date of assembly of the engine followed by a two and possibly three letter suffix code which indicates the specific engine and trans., and then a final vehicle assembly plant code followed by the last several digits of the VIN...that sequence number I spoke of.
So, if you see the engine stamp...ie: T0614EG Z 177205
T = Tonawanda engine assembly plant in NY
06 = Month of June
14 = 14th day
EG = The Only code used for a 66 Chevelle SS with 375 HP engine.
Z = Fremont. California Assembly plant, as example only ( of the vehicle)
177205 = Sequence number as described above.
The sequence number on that engine MUST Match EXACTLY with that which is on the VIN TAG on the door for this to be the orig. engine to the car. If the engine has the EG code, but the sequence numver is different, then it's an L-78 but not from that car. Also, the Assembly plant code, Z in this case for Fremont, should match the door vin....NOTE HERE... the TRIM TAG has sequence numbers also, but these are Fisher Body sequence numbers, never try and match the Trim Tag numbers with those on the engine.... the trim tag will have the assembly plant noted and of course if the TRIM AG has Baltimore built and the engine has Fremont ( Z ) then you also know it's not original engine. TRIM TAG code for Fremont is not Z, it is BF...that can be confusing too...
ALL 66 SS Rags got the 138676 Vin and all hard tops got 138176.
All 3099 built L-78's got EG Engine code, none got air conditioning and none came as automatics.
One has to consider that the 375 HP engine was the top of the line high performance engine, most ordering this Bad boy, had plans for it and wasn't to go get groceries unless the grocery store was at the end of the drag strip [img]/ubbthreads/images/icons/wink.gif[/img] so keeping that in mind, when these cars were ordered, they also came equipped with a trans and rear to support that power and quest for speed...did I say 4 Speed...yes, I did...as in most likely a Muncie M-21 or if you really knew what you were doing ( 12 people did) an M-22 Rock Crusher 4 speed. Gear ratio in the L-78 would most likely be low, as in 4.10:1 Posi Ratio coded as KK on rear axle tube, 4.56:1 Posi coded as KM, or 4.88:1 Posi coded as KO. again just things to look for when trying to rule in the possibility of a real L-78.
Radiators also got tagged according to engine size/HP and if it still had the orig. Harrison Rad and still had the Tag attached to the inner upper tabk...look for a two letter code "VM" for 375 hp car.
The L-78 was cancelled on May 11th 1965. and as such was not part of the 66 Chevelle production options when the 66 production year started ( July/August 1965) and early sales literature doesn't mention the 375 hp either. but the L-78 was re-introduced into the chevelle line up on October 7th 1965 at a cost of $235.26 what a bargain eh!
The block was a 4 bolt main # 3855962
Heads # 3873858
Crank was forged steel
Mechanical cam
Aluminum intake Manifold
Holly 4 barrel carb
11.0:1 compression ratio
Now, where else can ya get that kind of free info but on the Net...
Good luck and I am now back into retirement mode...Later!
mike