The answer to your question is "There isn't one"
There are a couple candidates that get close, neither has been manufactured for many years, and both are fairly rare to find.
Batten Heads: While not an exact match to factory 915 castings, these looked the most like stock castings, water jacket plugs in the ends, rough cast ends, etc. they would fool most anyone if painted orange. These were made back in the 1980's or there about, no longer made. They had some pretty well known casting issues, porosity, leaks, etc. Some were good, some were junk, total crap shoot. Most I've seen were already ported by someone, again, total crap shoot, it either improved them or turned them into junk.
Diamond W2 heads: These have rough cast ends which resemble cast iron when painted but lack the core plug on the ends that stock heads have, again, you'll fool a lot of people with these but sharper eyed Mopar guys will spot the lack of the plugs. These were made my Diamond Racing products back in the 1980's (Diamond is still in business making pistons but not heads). These were in the Direct Connection catalog for sale to racers back then, VERY expensive for the day, and good castings, the flowed BIG numbers if given even a mild port job. There were some reports of some porosity issues but I've had a few sets of these and all of them so far have been beautiful. Same story as Battens, hard to find, often ruined by previous porting efforts, etc.
The typical racer mentality seems to be "Who cares what it looks like if it works" but I feel there is a good potential market for a stock looking aluminum head, there are a good number of guys that I know whom would like to keep their car looking stock but would like to improve the performance.
*Batten heads shown on this engine
