Stan,
Just to set your mind at ease, the Factory Racing suspension system sold by Nissan Comp has rates of 218/778.
I use 225/approx 900 (cut roadster comp frnt springs.
I'm not sure this is ideal, but it seems to work OK.
As far as the oscillations you describe, I would look for:
-Front sway bar binding on frame.
-Struts bottoming out/hitting bumpstops
-Loose/worn/bent parts
-Drunk driver

I'm at [email protected]

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"Bad" Al Bell
ITC #3 Datsun 510
DC Region MARRS Series