Here's my take on this - don't romanticize engine components.
Realistically, if it has "historical value", then it probably shouldn't be used for racing.
I take it you're talking journal overlap on a crank that's had the journals turned down?
I had a similar situation arise with the Midget.
After I ordered up a custom billet piece, I found a factory experimental Formula Junior inline short stroke BMC A series crank on E-bay.
I doubt if thirty or forty of them were ever produced - truly a rare factory racing item.
I didn't bid on it, but I kept thinking, what a neat idea for the Midget - a limited production, factory forging just perfect for my application.
After lamenting over it, I shared my pondering with a fellow racer, who put me straight. The piece I had on order was a far superior item and a known quantity that raised fewer questions and doubts than any vintage specialty piece I had my heart set on. Practicality ruled the day, I ran the billet piece as planned, and had no doubts as to its durability.
The moral of the story is this - It's easy to romanticize the uber-rare and unique racing components of historical value. The "wow" and "cool" factors are always there. But if you want to race, go with the pieces that you don't need to worry about, the best pieces you can afford, and save the historically significant pieces for the Concourse de Elegance.
If it is historically significant, find the right buyer who's doing a 100 point restoration, sell it to them, and use the money to buy the piece that will get you down the salt without leaving an oil slick or sending you home with a windowed block.
