Possibly you are best to obtain these from forum sponsor Mits-Fix in Melbourne.
I have purchased a number of items from him.....all good.
He has complete, brand new, non-genuine distributors for $335.00($318.25 after ebay discount) including standard postage.
https://www.ebay.com.au/itm/Distribu...item2f0cc279cf
You can buy caps(aka covers) and rotors individually, but my money is on a failed coil, and I would replace the whole lot in one go.
I believe a unit supplied by Mits-Fix will also come with the correct size "O" - ring at the base of the distributor.
Most higher mileage 6g74 engines will have potential oil leak problems from the base of the distributor by this stage even if you have not removed and reinstalled the distributor due to failing "O" - rings.
Even if it is just initially a problem caused by failing cap or rotor, at some point in the future the coil and/or the "O" - ring will probably fail, especially after 270,000 km.
Just get it all in one go and minimise the headaches.
If you are on a tight budget he has complete second hand units for $90 incl. postage - 90 day warranty.
I imagine that your friendly local mechanic, if you have one, will not charge too much just to do a distributor R&R if you are worried at all about doing it yourself.
Whatever you decide to do, please keep all of us updated as to the eventual outcome.
Such feedback and knowledge is quite beneficial to all of us, but it is a procedure that sadly many new members do not follow.