Playing high ECL characters at lower levels

[DragonIceAdept]

I stumbled onto the Powerful Races at 1st Level variant rule in PGTF, for races with LA. Is there a similar rule for races with RHD?

[Saintheart]

Tried the savage progressions out of Savage Species?

[Powerdork]

As I understand it: You're meant to clear with your DM that you're playing a monster character and the specifics of it.
If you don't (such as if it's openly allowed by an organized play event's rules but not elaborated on) then the 3.5 core rules give you tentative license to play an unmodified monster (with any combination of RHD and LA as your ECL, but no class levels unless you're looking at less than 2 RHD, so it can be replaced). You use your ECL for encounter/XP/APL math, as normal, and you gain reduced XP relative to a Player's Handbook race as a result, and beyond that you need to meet the XP appropriate to a level higher than your ECL to gain a new character level, your first class level (and just to stress it again, this XP comes slower until your ECL is appropriate to the challenge you're facing).