From a Pantheon Productions magazine, Impulse 2 (1980) – while I have yet to ID the models, the photography is by Adam Cadman. I’m pretty sure these guys are also in one of the Impulse loops. (They’re on the box cover! But there’s some mis-matching between the VHS box, and the 8MM loop boxes – time to pull out the tape.)
edit: having just zipped through 2, 3, 5, and 6 – I am fairly confident it’s #1 – Steam, with Pete & Dean/Dan.