Block casting # and date should be on the flange where the trans. bolts on. Casting # is visible on the drivers side and casting date on the passenger side with a mirror. May need to move plug wires to the side.

Also ck. intake casting # and date. On the intake behind the carb.Correct # for a 325 or 350 motor with a rochester carb is 3931067.Intake for a 375 hp motor would be aluminum and have the number 3933163 and be for a Holley carb. What makes you think it should be a 375 HP car? A 375 hp. car in 1969 would have come equipped with smog, and AC was not available with the 375.

The 375 would have been a solid lifter motor.

The 291 heads are correct for a late 69 375 motor. The 350 hp. would have used the 3964290 or the 3931063. What is the casting date on the 291 heads, as these came out late in 69. Most 69 375 cars came with the 840 heads. The casting date on the heads needs to predate the cars build date.

Also need to look at the rear end code stamped on the tube on the front side of the passenger side about 3 or 4 inches from the center section. What is that #.

Also ck. the # on the distributor. Backside facing firewall.Stamped.May help to determine hp.

Thank You so much, the car had a aftermarket manifold so I'm replacing it with a stock manifold,carb.,dist. The date on the heads is May of 69 and the car was built in July 69 and has solid lifters.The car has the original 12 bolt positraction dif.The Quadrajet is 700 cfm and has huge secondaries and the carb.removed was a double pumper Holley so it will be stock once back togeather.This is a RPO radio delete car built and delivered in July of 69.Just concerned about the CFM

If it is a true 375 car, then it would have had the aluminum 163 intake and the 4150 holley carb when new.List number on the Holley airhorn would be 4346. Part number would be 3959164 GE.
Which quadrajet do you have? he 200 or the 204?

Purchased a 7029204 equivilant from Summit Racing

I am sure you know that the quadrajet won't work on a Holley manifold and vice versa. Holleys are square bore and quadrajets have bigger secondaries than primaries.You will have to use the cast iron 325 or 350 hp manifold to use the quadrajet. Hope you had this planned out.

Any idea of the required CFM on the Holley 4150 ?

470 or 500... your pick.

http://www.holley.com/HolleyCatalog/Catalog.asp?pageNumber=22

I would think more like 600 or 650 editions of the 4150 model Holley for the 375 hp, 396. The smaller carbs are for the 283 or 327 engines.

Different versions can go all the way to 850 CFM. I believe the 427 COPO cars came with an 800 CFM 4150.Boss 302s ran a 780 and boss 429s ran a 735.(if my memory serves correct).

Thanks and I just purchased the stock replacement series 4150 with the correct list number and it was a dual inlet Holley and 800 cfm for the L78 375 hp that I have. It was a true SS car and came with a 396 but not positive it was a L78 but it has a date correct motor so who knows.Thank You for all your help Jim

You are welcome Denny.Like somebody else posted earlier,I'd be looking real close at each casting and part #'s.That would definitely increase the value of your SS as well as confirm if it is a true L-78 car.Another thought,if your interior is all original there's a chance a build sheet may be lurking inside<g>.I'm not sure if Balt plant had build sheets or separate body and chassis broadcast copy sheets.Sounds like a good buy from what you've described here. Jim

Great idea Jim and I will sure check,the interior is for sure the original but the carpet mus have been replaced because it is not faded but I will be sure to check and my present goal is to restore the top of the engine to stock 375 specs