There are two different width rear oil pan seals used on the model A engines . The 28-29 seal was 13/32 wide , part number 9790 , the 30-31 seal was 3/8 wide part number 9800 .. Some model A parts catalogs only list one width . Brattons catalog lists the rear oil pan seals on page 48 of the 2017 catalog that I' looking at . It sounds like you've got the narrow seal that is too narrow to hold its self in place . I've never seen the need to glue the seal to the rear main bearing cap . If the correct seal is used the seal will fit into the groove of the rear main bearing cap plenty tight enough to hold it in place while the oil pan is being installed . The inspection plate and rear of the oil pan will push the cork seal very tightly into the grove on the rear main cap as the oil pan is tightened . All of the rear oil pan seals are too long and must be trimmed and fitted . The ends of the seal fits on top of the oil pan gasket , where the gasket fits into the groove on the rear main bearing cap . I seal the ends of the seal where it rests on top of the rear oil pan gasket tabs . If these tabs are cut off in a short cut attempt to install the gasket to the oil pan instead of the block CAN result in an oil leak that resemble a rear main bearing leak
. Just to add a thought , There is always a chance that the rear main bearing cap may have been replaced at some point in time . If the main bearing cap that came on the engine has been replaced it could easily have a 28-29 cap on a 30-31 engine and the groove size on the main bearing cap won't be correct for the model . When I get ready to perform such a procedure , I will have both seals on hand just incase . The rear pan seals are inexpensive .