Vintage Crane Siwelclo 1935 toilet repair - need help

I am trying to repair a toilet that is older than many of the users of this forum, i imagine.

I have a Crane Siweclo toilet from about 1935 made by Trenton Potteries.

I am getting water leaking between the tank and the bowl.

I tried making a gasket and also putting in a wax ring but neither worked. If i drain the water slowly from the tank to the bowl it is fine but when i flush, water starts to drip from under the tank.

I am attaching photos of the toilet - - the area where the tank connects to the bowl is very unusual and has an overal 3 1/4" by 41/4 opening.

Any ideas on this? Thanks.

 

One might ask why you are trying to repair an 80 year old toilet that probably uses 7 gallons of water per flush when there are dozens of up to date low flow toilets readily available for likely less than your repair parts will cost. But, maybe you still drive that '35 Ford. LOL

 

I wonder if one of those Fernco Wax Free Toilet Seals would do it. They have an adhesive top that you would stick to the tank. http://www.fernco.com/plumbing/wax-free-toilet-seal