If I look at the spinning blanks that are ERN posted and were to choose one with a ERN in the 13 to 16 range, would that be a reasonable candidate for a 10 wt or hier fly / spin convertible. If that makes sense then I have a recently purchased a 7 ft 3 piece spinning blank that when I tried to CCS ran out of cents trying to get the 1/3 deflection so it will come in 16+ERN. I am planning on using it if that sounds reasonable.

It would certainly cast a 10-weight line but not easily unless you can put a lot of that line past the tip during casting. The length may hamper your ability to do that.

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Rule of thumb - 10 over 16, then reduce to get you into the ball park . Equals a 5/8's lure weight.

Bill - willierods.com

John,
If the rod is that heavy it may be a real chore to cast a 10 weight line on.
You may be better up-lining to a 12 weight tarpon line to obtain a reasonable casting distance.
Even at that the blank will still be under-lined by about 2 sizes.