Steve Perrin's Quest Rules are an extension of the RuneQuest ruleset by one of the original author's of that latter game. In addition to using the core features of RuneQuest, SPQR also uses a point-buy system, benefits and disadvantages (both of which are derived from the Hero System or GURPS), a degrees of success system (derived from the various White Wolf game line), and a skill system with "overskills" and specialisations with varying difficulty levels (the latter, again, from GURPS).
Questworld was a gateway-RuneQuest world released by Chaosium in 1982. It was meant to be developed by RuneQuest players as a gateway alternative to Glorantha with an open invitation for further development and publication - but no further releases ever came out!
Some of the features of Questworld included several small continents which did not interrupt ocean currents; thus allowing rapid travel. Each continent has tactically placed mountain chains allowing for a surprisingly wide variety of climates.
A combined playtest of the SPQR ruleset using the Questworld setting is being conducted at RPGReview. One may join the mailing list for participation in both the rules and setting development.