Using a 260A engine model should get you what you need.
Volvo T/Housing part number
855485 = 855470 evident if you zoom in on this photo,
http://www.boatersland.com/vlp855485.html
Volvo thermostat part number
876305 fits the 260A,
http://www.volvopentastore.com/Cooli...view_id.783506 < Also don't forget items numbers 36 and 37.
Genuine Volvo Penta Thermostat Kit V6 & V8 AQ Series Engines -
144? (degrees) Fits Volvo Engine Models: ◦ AQ175A AQ205A 430A 430B 431A 431B◦ 432A 434A AQ190A AQ200B AQ200C AQ200D◦ AQ200F AQ211A AQ225B AQ225C AQ225D◦ AQ225E AQ225F BB225A BB225B BB225C◦ AQ231A AQ231B BB231A 500A 500B 501A 501B◦ AQ240A AQ255A AQ255B AQ260A AQ260B BB260A◦ BB260B BB260C BB261A AQ271A AQ271B AQ271C◦ AQ271D AQ280A AQ290A AQ311A AQ311B 570A◦ 571A 572A 740A 740B OEM Volvo Penta part #876305 Replaces Volvo Penta part #876305-4