exhust leak 89 mustang

[10yrplan]

when starting my 302 i find a exhust leak coming from a port in the back of the heads. looks almost like a pipe used to go from head to head maybe for some kind of a bypass. the engine is carbed and out of a truck. can i plug these hole so i no long have a leak and will that plug cuase damge do to backprussure in the head?

[rednotch]

http://www.store.partsdinosaur.com/product1521.html

yes you can plug them. its just the thermactor ports for the egr system.

[10yrplan]

thanks