MaxG
If you are going to be using heavy long belly lines then 5" may be necessary if it is a large arbor. That, of course, would depend upon the manufacturs"s definition of large arbor. I have a Peerless 4A (small arbor, click drag) that will take any line on the market + a minimum of 250 yards of 30# backing. Useable spool space on that reel is approx. 3 3/4 deep and 1 1/4 wide. I know you are not looking for click drag, just using it as an example of capacity.
So Large Arbor:
Fast retrieve(good thing)
Reduced capaciy relative to size (may be bad thing)
Mid Arbor: Fast retrieve, larger capacity relative to size
Small arbor can be fast retrieve IF it is big, wider spool and the fish does not rip you for 100+ yards of backing.
I am sure others may disagree, but I stay far away from cork. If it is very well sealed you may be OK. If the cork is exposed and the reel gets wet .... Imagine that when fishing ... You will have a problem. The cork has to be lubricated or it will shred upon rotation when compressed against harder surfaces within the drag system. Wet greased cork is not well known for generating any sort of friction at this point .... can you say free spool.
I use reels with click pawl or well sealed carbon fiber. My test of a new reel is to set the drag to support the reels weight. Put in a container of water, come back an hour later. If it slips it goes back, if not, its a keeper.
So all of this pontification to say ... Dealers choice
Tweedside,
This may be an option for you, although I do not know the wait time, but it is probably less the the average of 2 years from Bogdan.
Go to 3w's.westslopefly. enter the fly reel section and look for the Kineya model 705. At 17.6 oz (500 grams) it may be heavy enough to meet your needs. While you are there you may want to check out Ted Godfrey's Salmon III at 12.5oz it may be too light for you.
Rich