double valve spring, etc. questions

[Lizirbydavis@cs.com]

I'll putting double springs on my early cylinder head.  Do I need to put a 
lower collar on the inner spring?  Does the stock upper collar work?  Also, 
does 
anyone know if there is any significant differences between the TSI springs 
(89.95), the Richard Good springs (75.00), and the BPNW springs (58.00)?  Does 
anyone Have an opinion/or has installed Richard Goods valve guides with the 
Teflon seals (89.00)? 
Joe Davis