Welcome NHblacksmith,
I've had good luck using refractory cement. If you're ever in the Lewiston/Auburn area the people at INFAB have all kinds of it. Various bricks of different strenghts too. I use the cement for furnace castings as well as lining the old Buffalo forge firepot.
You might consider a big truck rim for your base, give you a good excuse to visit your local scrap metal man too. Allways a good day for me. Remember, life is like a box of chocolates. Let the world take another turn and try again.