Hi
Your first click should be to
http://www.theanalogdept.com/Nice deck, if you remove the TP13 and put it on the kitchen scales it should weigh about 250gm. The arm board is about 150gm. Your new arm and board should be close to the total wt of these originals, if you want minimum fuss/hassle setting the suspension. Dealers also used to counterbalance slightly heavier arms with a ballast weight on the front corner of the arm board.
I've never had a Rega to try, but word on the net indicates it is not the best match. I have no idea why.
Historically SME arms were a popular choice from day one for this deck. Mostly 3009.
Linn arms like LVX and Akito are economical second hand and recommended by many. I certainly have no problems with my 150/LVX/VMS20e, great combination.
I have recently replaced the Linn black springs I was using with radiator hose as recommended by Steve at the Analog Dept.. The absence of bounce is disconcerting at first, but it is quiet and sounds very good. Reminds me now of the many listening sessions I had with a TD124 during the 80s. 2 decks in one! This alteration also removes the problems of fitting a heavy arm and presumably obsessing about dressing the arm cable.
Allegedly the original and best tweaker of the 150 was a guy called Hamish. His deck took the design Thorens had dropped for the 160, beefed up the springs, plinth and top plate, added a bearing and the rest as they say is history. Should be honoured posthumously.
Linn bits, like springs and belts, fit the Thorens - a quote I really like from the AudioKarma site - 'TD150 is grandaddy of Linn'.
Hope some of this is of interest.
Regards