[poncho-mike]

What are the part numbers for standard 455 Trans Am exhaust manifold p/n's.

I've seen Ebay ads listing 490142 and 490149 and 490142 and 490143. The Wallace racing website only shows the p/ns for the higher performance versions.

[jwcfbd]

does this help? https://www.teufert.net/pontiac/exhaust.htm Looks like 490802 and 490803
https://www.teufert.net/pontiac/page2.htm

[SD73]

My '73 parts book shows 490142 and 490143 for the D port manifolds. jwcfbd's numbers are correct for SD heads.

[unruhjonny]

standard exhaust manifolds have been for the last thirty(?) years quite overlooked;
When I first came to realize this, I also found that getting hard information on numbers ect was quite tough.

I have a small collection of them and am happy to share the casting numbers that I believe to be applicable:

drivers: 490149 (my example is from a 1974 model year casting)
passenger: 490142 (I have both 1973 & 1974 model year dates; I have this casting number even in a 1976 calendar year date)

As far as I can recall, I have had several drivers side manifolds have the bolt bosses break in half from trying to remove damaged or broken studs - so I currently have more passenger side than drivers side;
I believe I have more variety in drivers side casting numbers.

By 1977, both sides used three exhaust manifold to exhaust pipe studs;
In 1973 they still both used two studs per side.