replacing tonearm question?

Simao, it all depends on the geometry of the tonearm's and their base configuration. You have to take the Sumiko off and look at the hole size in the arm board. If the Jelco requires a bigger hole or a slightly different position to get it's overhang right you will have to enlarge the hole then see if you can mount the Jelco without an ugly result. The cleanest way to do things is always by getting a new arm board which I am sure VPI can supply. You can also make one yourself by using the old board as a template. If you do not have the capability to do this any wood worker with a drill press can do it for you.

Thank you, mijostyn. My existing armboard is acrylic and there's a discussion either here or on the Hoffman forums with links to a shop that could make me a new board. Would you recommend acrylic or wood?

The pivot to spindle distance of Sumiko FT-3 is 221.7mm, and the Jelco 750 and 850 is 240mm. I think a new armboard is required unless you use a tonearm with same geometry (e.g. clearaudio) than you can use the existing armboard with some work.

https://www.vinylengine.com/tonearm_database.php