I'm doing a ground up restoration on a 1970, 2.0/6 and I'm striving towards originality. Engine and trans are original. Rebuilt but match the COA numberwise.

I know the Marelli came stock but has an unobtanium issue with the cap and rotor. When you CAN find a part it comes with a tube of KY Jelly. There's one on eBay right now $350. link

Is it worth it? Or is the Bosch the easiest thing to do? Not that I'm going to compete in a Concours but do they ding you for not having the correct dizzy?

Get the right dizzy, keep it complete and stock.

Call a few of the shops that fix them...HPH, Jim at Easy, AA, local to you porsche shops...

You should be able to find one at a reasonable price.
Jim at Easy would be my first call.

Rich

If the dizzy is your last 0.1 point in a nationally judged event, it may be worth it to you. My Euro /6 had a Marelli which I believe was original. My US /6 had a Bosch by the time I got it, and I donno if it was original to the car or not - there were a few things on that car that weren't.

Nowadays most PCA concours are cleanliness events, not originality. There are few judges who would know what's correct. I had a Parade judge ask me if the drilled & wired CV bolts were original...

(Do you have original, factory-applied paint? Do you have period-correct 165-series tires?)

Just stuff to consider...

My 70 -6 had the Marelli distributor, but when it started going south, I simply replaced it with an easily serviced Bosch unit. You have to be sure to get the correct one, but will be happy with it.

Keep the original Marelli in a box (along with the removed throttle positioner, etc.) for some future concours weinie, and enjoy driving the car in the meantime. It is a simple bolt in conversion, so you're not destroying anything.

A functional upgrade like a good distributor (Bosch) for a marginal one with scarce replacement parts (Marelli) won't detract from the value of your 6. As George said, unless your car is a national concours contender, go with the better part.