These are all versions of the proposed launchers with a turbopump rather than pressure fed second stage, and the version on the right uses a fairly standard, albeit uprated Black Knight. It suffers from having a 3 foot diameter and a height of nearly 60 foot!
This is the squatter 54 inch Black Knight, a design that was later apparently dropped in favour of a version that did not taper down to the engine bay. Payload is increased.
A six chamber Black Knight, again of 54 inches. This limit was imposed by the ground testing facilities at High Down, and it is interesting to note that the 4 Stentor motor version was rejected on the grounds that it would need a wider first stage.
Now an 8 chamber Black Knight, again of 54 inches. This is almost Black Arrow size. Now the payload is calculated at 377lbs, which makes it really makes it the only version worth considering.