Starting in the early to mid 60's the planes started getting bigger , requiring more power (shark 45,Colossus, etc.). Engines such as the K&B45, Veco45,ST60, were tried. What other power plants were used to haul these larger models? Were there many custom bored and stroke units being built and used?

ST 60 was produced during the Classic era but it was not used in any appreciable numbers - at least not in the USA and not to any effect on national level.  For big power the engne of choice was the Fox 59.

The ST[40-46 came out in the mid 1960's and they had the power to pull big models.Quite a few years  later the the ST/60 was put in those same models
Ed

Hi Denny:

No, this one never was published. I don't think Bob has the plans for it still, but I'll check with him about that. Yes, it would be a great choice for Nostalgia. But, and here's a thought..., the Classic rules read that a model must have been designed, built, OR flown - not AND flown - prior to the December 31, 1969 cutoff date. If Bob had designed the ship in 1969, and/or began building it before Jan 1, 1970, then it is indeed legal for Classic competition. That is the case with the Oosa-Amma (Original Stunt Machine - the one before the published one...). It was designed and under construction in the fall and winter of 1969. It was not flown until the spring of 1970, but it is still legal under the rules.

Later - Bob Hunt

I forgot about my own model from 1965 "The Jet" It had a Fox59 in it. I still have the plane and it is a very good flying model. I flew it last year with a ST/46 in it. I even had a ST/56 in it for a short time many many years ago
Ed

I think Windy used an OS 60 in the Sweeper.

Best,        DennisT