I do have the conversion chart on sheet 7 of the MS plans, but it only covers rope not the thread. After further research what I have discovered is that MS is using a flying tackle thread, mostly only available at fishing tackle stores and obviously on Amazon. The weight is 3/0 which is stronger than the typical sewing thread found in Hobby Lobby and sewing centers. The problem ordering online is that for one thimble costing $3.00 the shipping can be $8 - $10!
I did talk to Chuck at Syren and his thread is .008" diameter vs. .005 for the 3/0 weight thread. Chuck did recommend, however, using a standard sewing thread as being sufficient for most our needs.
I believe I have all the answers now for this topic and appreciate the help and comments from everyone.
Thanks for your help.