I am a fan of the stand alone boiler because they are so versatile . You can mix and match boilers and engines and You can have any number of engines without having to have a like amount of boilers. Here are mine. There is a Wilesco D16 , a Jensen 75 and a Jensen 70. As you can see, they are all modified with 3/4 " plywood bases air gapped to an aluminum mounting plate . The D16 and Jensen 75 are gas fired , while the Jensen 70 is of course electric. I use PM research unions on all my boilers and engines so they are truly universal. The Jensen 70 is the most used of the three because it is just so easy to plug in followed by the little Wilesco , which really does steam well. Here are a few pictures.
D. E. Jones