1978 318 heads? Small port? Or large

Negative. Chrysler never used the 360 port size heads on the 318. Not even on 318 police cars. They simply slapped the 360 4 barrel intakes on them.
For 318 Quadrajet or Thermoquad police cars with the 360 intake and the ELB or E48 code on the fender tag?

That obviously applies to trucks and vans with different codings though. Every person I've talked to who took apart an original motor had 360 cast # heads to show for it. Never had one myself, wouldn't mind to but don't care. There even seem to be certain casting 360 heads that the 318s usually got that overlap with lower performance 360s that had IIRC had higher factory compression ratios than the performance motors.

Some of those vehicles with those 360 cast heads were also fairly low miles. The factory's even got the compression ratios listed for the 318 4 barrel motors- they were all down where the 360s were instead of where the 2bbl motors were. How did they drop .2-.4:1 with the same heads and pistons?