All stats named the same are the same , WIS = POW, Size - determine from the characters described size, or roll 2d6+6, or take an average of STR and CON.
Persistance = 10 + POW + (5 x base will save bonus)
Resilience = Con + POW + (5 x base Fortitude save bonus)
Dodge = Dex +10 - SIZ + (5 base Reflex bonus)
All skills known by character at Base + (5 x skill ranks) (find a fair equivalent)
Combat skills - all weapons regularly used by the character have a skill of
Str + Dex (or just Dex for missile/martial arts) + 10 x Base attack bonus. If the character has shield proficiency give them the same bonus.
Feats - give them an attuned Rune for each feat they know , ideally a relevant rune to the feat. If really powerful, look at legendary abilities.
Spells and extraordinary abilities- will need to be carefully worked out depending on class, but thats beyond the scope of a fast and dirty conversion like this.
And amalgamate several feats into a single Legendary Ability. I was wondering how to handle feats and whilst some match pretty well (Weapon Focus() to Metal, Improved Initiative to Disorder, for example) others struggle. With the skill bonus feats it might be better to translate them as a direct additions to the basic skill of the character - after all, all such feats do is enable the character to bypass the level+3 limit for skill ranks.
It's worth looking carefully at the synergies, too, to work out whether or not they should be translated to %ge additions.
As Runequest is a general skill system rather than a class/level based system I think 10% per BaB is about right. Remember BaB does not include any stat bonuses. A wizard with 12 dex, 10 str would have 72% weapon skill at L10 (+5 bab). Given that 60% is easily achievable by a RQ beginning wizard character (20 in stats, +10 bonus to skill from cultural background, 30 from free skill points) I dont think that is at all unreasonable.
Also that is 72% before you deduct armour penalties.
Yes, that seems a fair compromise - i was tring to root mine more in RQ character generation. Mine gives a L20 fighter about 230% chance atgxtg gives them 150% - depends which you think best represents the top end of Power level. A L20 fighter will be routinely beating up Giants , something that the average RQ character will find pretty tough