I found this about the DOHC Hemi from www.allpar.com/mopar/hemi/hemi.html
no pictures though

Dual overhead cam HemiA 426 dual-overhead cam Hemi was actually produced - two of them, in fact, and both were made in 1964. The DOHC Hemis were made to counter Ford's response to the 1964 426 Hemi, the 427 SOHC, but when NASCAR ruled against Ford's engine, there was no need for the overhead-cam Hemi.

Neither of the DOHC Hemis were ever placed in a car; one was destroyed, the other moved to the Kansas City area. (source: Muscle Car Review. Thanks, Stéphanie Dumas.)

An article by Tom Shaw in Mopar Muscle went into considerably more detail. The DOHC Hemi was project A-925, and it would need to be much more powerful than Ford's SOHC 427, but still rugged enough for racing - and able to conform to NASCAR's rules. Two possibilities were seriously considered, according to Shaw - one using two cams positioned between the heads, in the "valley;" four valves on each cylinder were operated by lifters, pushrods, and lifters. This expensive setup was considered to be a contingency plan and was never actually created. Nearly as ambitious was an engine with aluminum heads, dual overhead cams, and, again, four valves per cylinder, with pent-roof chambers. (Chrysler had been working with four valve per cylinder engines for a never-completed Indy run in 1963.)

The dual-plane intake manifold had eight runners per side (Chrysler was heavily into efficient and innovative intakes) and made of magnesium - but designed for a single four-barrel carburetor, as required by NASCAR.

The cams were driven by a cog belt, using external cog wheels at the front of the heads. Because the cams were directly above the valves, valvetrain mass was low, so the engine could rev high - a 7,000 rpm redline was specified, high for the era.

Shaw noted that no DOHC Hemi ever ran under its own power; they were driven by an electric motor to check the valvegear functioning. Research stopped in 1964 when NASCAR banned the SOHC 427 and Chrysler's own race Hemi. One DOHC Hemi still exists.