when i installed my new 30 plate fphe this afternoon, both heater hoses, feed and return, on my 1980 240 D, were 3/4 and not 5/8 as "everyone" always says on the forums.....i had to run all over town and find 5/8 to 3/4 hose adapters to make it work on the fly with the hardware i had ordered from around ebay......it works perfectly now, and is extremely heavy and u can tell its well made....and my wvo is burning hot as well as my heat in the car
cost 80 bucks plus tax and shipping, from a company called WVO Designs.....i would recommend them....
http://www.peachparts.com/shopforum/attachments/alternative-fuels/110318d1364085718-install-oe-bosch-style-prefilter-after-30-plate-heat-exchanger-30-plate-heat-exchanger.jpg
http://www.ebay.com/itm/281058565816?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649