Those may be SCE Accu Seal Pro Intake Gaskets as they have orange sealing rings around the ports. SCE lists two different port sizes for 400-455 Buicks with stock location ports, both .062" thick. P/N 271101 are listed as 1.100" x 2.375", and P/N 271104 at 1.220" x 2.520" .
The link below list all SCE Intake Gaskets for 400-455 Buicks.
http://scegaskets.com/Buick/400-455-...kets/tc257513/