66 - 273

numbers block is a myth on a 66. There are no VIN stamps anywhere. Just get it close date wise. But you have it already so your good. 66 is a good year for mods as it will take a 'normal' LA intake but if your looking for 'numbers', youll have to find a 273-4 intake from a late 65-to mid 66 year date coded intake. 66 year was manufactured from about Aug of prior year so a 65 dated intake will work IF the bolt angles are correct, ie there are no wedge shaped bosses on the intake bolt holes that would bias the thinner 5/16 bolts toward the crank center line. Your looking for flat bolt bosses that go straight through the intake flange. Get a modern cam that will take your lower compression into account. The stock 273-4 cam was designed for the higher compression of the 4bbl pistons used in any 273 block, they did not change. You got 2 or 3 choices for chassis headers, Dougs, Ed and TTI. Make sure you get the 318 port sized headers, 340-360 flanges will not seal. AS stated headers are not the most practical upgrade her on a mild build. Just use the larger Y headpipes and Formula S type exhaust as it was a pretty good design.