PowerMac G4 533DA & HDTV - video resolution / refresh rate problem

Question

Hope someone can help, I need to access more resolution / refresh rates than I currently get in the Leopard display control:
I have a PowerMac G4 533 Digital Audio running Leopard 10.5.8 (unsupported).  It has an upgraded AGP videocard, a ( flashed PC - RV200 chipset) Radeon 7500 w/ 64MB and a DVI output w/ a VGA adapter.  I have used this Mac perfectly with my 19" widescreen Samsung SyncMaster 940BW, at a resolution of 1440 x 900 / 60Hz / millions of colors.  This monitor is actually for my MacPro, but I used it for the G4 to set it up.
I  moved it to my living room to use as a basic HTPC.  Since it runs Leopard, it has up to date VLC, Quicktime for video files and a working Superdrive for movies.  I don't expect it to play anything more than 480p properly, I think that was the best I got on YouTube.  But if I have a DVD ripped to DivX or MP4 it plays them fine on the Samsung monitor.
I connected it to my Viewsonic N3760w 37" 1080 HDTV.  It turns on, gray screen w/ Apple and gives me a working desktop.  The problem is that I cannot get it to give me the correct resolution and more importantly it seem to have the wrong refresh rate.  It is currently set at 1280 x 768 / 60Hz / millions of colors.  The screen give me like a small line slowly moving up across screen, higher refresh rates only make it movie faster up the screen.
According to my Viewsonic, these are the resolutions for computer using the VGA plug on the tv:
PC - 1360x768 (preferred) , 1024x768, 1280x768
Mac G3/G4/G5 - up to 1280 x 1024, 1280x720 (preferred)
Please note all of these are lower resolution than my Samsung monitor.  My Viewsonic also has on screen adjustment of " phase " and " frequency " as well as the usual color, contrast, etc available.  Is there a 3rd party app to manually adjust the resoluion and refresh rate?  I have seen Windows programs, does one exist for Mac OS X?
TIA, sorry for the long post

Answer 1

My Viewsonic also connected by VGA, no problem.
I wish I knew more. I checked out the app you did a trial of. I noticed this statement on their web site:  Quote
"After rebooting monitor stays blank
For some reason your monitor does not accept the installed frequency. SWITCH IT OFF!"
This is the type of statement that would 'worry me.' -- having the phrase: SWITCH IT OFF! all in caps seems to imply a possibility of damage...which I mentioned in my initial post. (and the site goes on to talk about how you should even then connect another monitor to change the settings you've made that were not accepted).
As I said, though, I wish I knew more for sure about this. It seems that you not only did the obvious of checking System Peferences>Display, but also realize the Viewsonic has buttons that can influence it's screen image, most about position of the image on the screen but at least one item about resolution on mine. (under Setup Mode)
For what it's worth, my Viewsonic is about 6 years old now, still fine, and has eight (8) possible resolutions shown in System Preferences.
Re: Your numbers.
It is currently set at 1280 x 768 / 60Hz / millions of colors. 
PC - 1360x768 (preferred) , 1024x768, 1280x768
Mac G3/G4/G5 - up to 1280 x 1024, 1280x720 (preferred)
If you're only talking about a difference of 1280 x 768 and G4 1280 x 1024, perhaps just stretching the picture using the Viewsonic buttons is the way to go.
Or, from the numbers, perhaps the G4 just wants a resolution closest to it's preferred state!?
Anyhow, good luck.