double valve springs will allow you to run at higher revs (more) safely. this is to prevent valve float.

rocker locks prevent the rocker arms from moving sideways on the rocker shafts (as opposed to the spring providing minimal force to keep the rockers put)

the rocker locks are relatively inexpensive.


if you decide to get double valve springs you will have to have new (later) valve guides installed in your cylinder head, as 4 of the stock ones are too fat to use with doubles
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1974 2002 R.I.P. Sawed into pieces
1969 2002 Automatic "Pumpkin"
1974 2002tii #2782677 (almost done being assembled)