Need help converting 3.5 to PF (Doppelganger)

[TabletopGamer]

I got this idea based off the Centaur in both series. The Centaur is a 6 level progression in 3.5 but is only a 28 RP in Pathfinder roughly meaning at lvl 1 it would have a CR of 1, same as the Drow Nobel which doesn't actually change your CR to much maybe a 1 level difference depending on how the GM reads it.

The Doppelganger however has 8 levels of progression 4 HD and a plus 4 LA
How would this translate over?

The Centaur lost a +2 to Str and Con and a +1 on Natural Armor and +10 ft on speed in the conversion.

[Debihuman]

I got this idea based off the Centaur in both series. The Centaur is a 6 level progression in 3.5 but is only a 28 RP in Pathfinder roughly meaning at lvl 1 it would have a CR of 1, same as the Drow Nobel which doesn't actually change your CR to much maybe a 1 level difference depending on how the GM reads it.

The Doppelganger however has 8 levels of progression 4 HD and a plus 4 LA
How would this translate over?

The Centaur lost a +2 to Str and Con and a +1 on Natural Armor and +10 ft on speed in the conversion.

Actually there is no reason to convert. They're essentially the same game. PF is slightly overpowered 3.5.

Debby

[TabletopGamer]

Pf does not have LA and so needs to be converted for PF

[Debihuman]

Why not just us the PF doppleganger in the first place?

Debby

[TabletopGamer]

That was grants a +8 to Str and a +2 to every other ability sore when D&D has a +2 across all ability scores.
Also they don't have detect thought and so forth.