If on passenger side there are probably both
If like most diesels the intake and exhaust are on the same side of the block, so yours are combined like everyone elses. Intake and exhaust on the same side. Regardless the block heater plug is on that side about midway, but once again I stress to have a spare gasket to replace the one you may have to remove in order to get the clearance needed for this job.
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan