I'm trying to find a Soundwave head (preferably G1-cartoon-style) that would be suitably sized for an Alternator. I'm not sure if there are any characters out there of a similar size scale with heads that look like him, but I know that the actual G1, Actionmaster, and MusicLabel heads are not good fits. Maybe there's a knockoff out there, too?
If this is for a custom, you'll want to head on over to Radicons, where you'll find a bevvy of advice and a pretty good selection of repros. Sculpt-Bot is our resident "head man," you might want to shoot him a PM. Ken
Some people do like the G1 head for this, but a lot of people have used the Cybertron Soundwave head for their custom alts... might want to poke around in Radicons a bit.