That's sort of a "how high is up" type question
Depends on the rest of your set-up and how you intend to use you car specificly.
They aren't 'to big' - if;
* you have the cam and valve train to flow them
* you have the exhaust system to support them
* you have and intake matched to they flow needs
* you have the gearing to support the higher RPM band to get useable torque range
* you don't mind RPM'ing the engine for standard street uses - or - you intend to mainly race the car and can keep the engine in the required RPM range
* you can live with the higher Idle required
* you don't need much Vacuum signal for brakes or accessories
I think you get the idea.
They're nice heads for the right application, but will be 'to big' if your intended use falls out of the above by very much.
You are usually 'money ahead' to spend your dollars on well matched parts for your intended use and needs vs. picking up 'cool' speed parts used.
Unless you intend to go much farther with your build in the near future you can get by with a much smaller port.
You might want to look into GM or aftermarket Vortec's for a nice reasonable head choice.
They have @ 170cc port and flow in the low 200's (@225) with a .490~.500" lift.
They will support HP in the mid 400's with the right cam and exhaust.
Hope this helps ...