I disassembled an engine with the above combination.  The heads were EBV.  Johns site lists them as having 1.78 in. intakes but these had 1.64.  There was a late 2 bbl intake installed.  Looked like it sealed but barely.  Two of the narrower seal points measured .085 inches and .061 across.

This almost certainly was a throw together job by a large rebuilder.  Rods were EBU.  Head bolts a mixture of grade 4 and 8.

But the engine looked like it gave full service.  There was a 4 speed trans with hand brake around drive shaft, so it would have been an F350 up truck.

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

the block i saw was ECK with a 54 head on one side with the small plugs and the other with big plugs and 55 intake.it ran fine and had a fair amount of miles.

I've been wondering how these early heads cc.  Will find out soon. 

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

might have been a 500-600 256 cu. in. used in buses and dump trucks, 54-56.

 lincoln/merc. y-blocks &mel's                                                               bucyrus, ohio.

Certainly shows why you shouldn't mix early with late heads/ manifolds. Those manifolds were barely sealing.

A friend of mine had a 312 rebuilt with "G" heads. When it was all back together, it did not want to idle at all. Turned out to be that the "mechanic" had used early small port gaskets which didn't even come close to sealing. Sort of proves that you have to check everything.

Regards

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

yalincoln, the pictured heads were on a C2AE 292 block . 

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.