I picked up the clear white pine for the mizzen mast and the main yard today. To answer my own question from a few days ago, there does not appear to be any difference between clear white pine and Monterrey pine. The material I picked up today looks exactly like the Monterrey pine sold as "Select" in the big box stores.
Still too cold today for effective wood-working. I was able to fabricate a "Center Line Marker" fashioned after a spar gauge but with a single pencil centered between two guide pins. When I use this simple tool I'll take photos.
In a recent WBF thread regarding building small masts, one respected poster stated the birds-mouth method is easier, faster and less fiddly than rounding off a solid or glued-up blank. I find this difficult to understand. It seems to me to be a lot of fiddly work involved in building a birds-mouth spar. This may be because I have very little experience using a table saw. But… I'm willing to learn. I am planning to try the birds-mouth method for the mizzen mast and, possibly, the main yard. Whether I use the method to build the main mast will depend on the success of my efforts with the smaller spars.
Not having a table saw is an issue. I don't have one and I have precious little experience using one. One possibility, at least for the mizzen mast and main yard, is to take the lumber to a friend's shop for ripping and cutting. I'll have to ask about using his saw and recruiting his help.