My understanding is they came with both.
Holden has had lots of odd specials pop up over the years that with the internet, have become documented as fact these days.
I did a quick google thingy and here are some replies. on the subject.
1.
I have a HR X2 factory opel 4 speed, Yes it has been on many hoists to confirm factory 4 speed, so many people say they don't exist, only came out in 186s hr not x2,,,,well they are only repeating what they have been told, they are WRONG, i bought car from owner who bought it new in 1966 off the show room floor when he was 25,i am Holden mechanic for past 45years,yes i have seen 186s 4 speeds, mine is build no;267s,first 2 weeks of production, its the only x2 4 speed i have seen,everything i read says it doesn't exist, any positive info would be highly regarded, anybody stating they don't exist, please put money were mouth is as i would happily put up $5000 for a bet, regards Nev.
2.
"The opel gear box was available about 4 weeks prior to the 186S option. So you could get a HR X2 Opel four speed factory car."
3.
X2 HRs with Opel 4-speeds are known to exist, I've verified a few myself. As mentioned above, the 4-sp box appeared on the production line a few weeks before the 186S, so a few X2s got thru with 4-sp fitted. The few I have identified have all been in the narrow engine number prefix band just prior to 186K162701 (the first production 186S engine no.) This all occurred in July 1967.
