Its good to see this thread active again.
Here is a bit of a summary of the info I've gathered on these trucks. Some of it is unfortunately a bit of guesswork and assumption but i think most of it is fairly correct.
There were, to the best of my knowledge, 4 trucks built. They were the following:
1/ the first #70, build date approx. 1960. Mack standard axle running gear, 1400 tires, DD 12v71 engine, all 4 axles powered, articulated in the center with a large transfer box supplying power to the front and rear bogies. This one was built by Basil (Barney) Oldfield in his shop on West Saanich road. The shop is still there, looking much the same as it did over 50 years ago. The final disposition of this truck is currently unknown. It did not, again to my knowledge, tow a pup and was smaller than the other 3 trucks to follow.
2/ the #36, build date approx. 1964. Drivetrain consisted of planetary axles, 1600 tires, probably DD 16v71 (I've heard it may have been a 12v71 as well), all axles powered, articulated in the center much like the first truck. This truck was built, again a bit of guesswork here, by Basil Oldfield and Butler Brothers in a hanger at the Victoria Airport. On Spirit's Website you can see the truck outside a large building with FAIREY AVIATION written on the side. This was most likely the roll-out photo-shoot.
This truck was probably the longest surviving one, well into the '70's. It towed a pup trailer later in its life. In the mid-70's it received a front end and cab almost identical to the later Mark 5, which changed the look of it a great deal. It was with that cab that it ended its days. It was sold by Butlers and after working on the island for a short time it ended up on the mainland coast. It is pretty much down to the cab and some of the bunk structure and turntables for the axles being all that is left. Reportedly, the axles went under some re-built Kenworths.
3/ The second #70, build date approx. 1967-8. This truck was similar in appearance to the #36 and was also reportedly built in the hangar at the airport by Oldfield and Butlers. Although similar to the 36 it had straight axles and some different details around the cab protector and cab area. Like its "sister" it towed a pup and was worked hard for about 8 years at the Butler operations in Sooke. It was cut up by Butlers at their machine shop in the mid-70's, reportedly with a cracked and twisted frame that was not repairable. It was used as a bit of a study model for the building of the last truck - the Mark 5.
4/ The Mark 5 (also given the number '70'), build date 1974. This was the final and biggest, very different from the other three. Due to changes in regulations and also technological advances in drive components, Butlers built this one with a rigid frame and twin steer front axles. It was built by a team of Butlers people, it was designed from the outset to max out the design. It was built in the old Butler Brothers machine shop - which unfortunately was recently knocked down to make way for a housing development. Story goes that the build team knew some of the local constabulary and when it came time for a test drive they made a phone call and promptly got an escort. Not like today where you'd have to get permission from 30 levels of mindless bureaucracy before you could apply for a permit to apply for an escort! Specs were: DD16V71TI engine (750 hp), Dart front axles, Allison trans, Clark BD121000 rear axles, 1800 tires on the front, 1600 on the rears (the difference in tire size was due to the load rating required). It was designed from the outset to haul over 100 tons and tow a trailer loaded with 100 tons as well. The custom designed trailer was built by Columbia Trailer and had 1600 size tires.
The Mark 5 is the one most often referred to as the largest logging truck ever built. It is also the one that many saw in MacBlo colours for awhile in the late 70's. It was built as a pilot project for a new breed of hauling truck with some consideration given to marketing it to the mining industry. Unfortunately, the plans for producing more of them never panned out. It was eventually sold to the same operator that had purchased the #36. It now sits (as seen in the photos on this site) in a boneyard on the mainland coast. The front axles are still there but the rears, the engine and much of the other drivetrain has been long ago parted out.
While all of these trucks share a common shape, they are all quite different from each other. Over the years because of this similar shape, some confusion has developed about what truck went where and which one had this or that. I hope most of the info I've given above is accurate but as I've found in the last couple of years delving into this - there's always another wrinkle to the story.
Thanks to Spirit and others for the loan of photos and info to try to get this story down. I'm still trying to get a more accurate picture of the life of each of these trucks and in time i will update this story.