Philip - no plans are needed from us - you have an idea already - choose the size of rounds, ovals etc. - cut those sizes in half (the cross section)and that is the pattern for the edges of your swage block. Same goes for the inner holes if you need them. Ok -just say you want a 8" x 8" swage block 3" thick - draw it out on paper(a 8x8 square) sketch in the sizes you want ..... simple as that
take this to the foundry and they will make the pattern for the object to be cast or refer you to someone who will ( most times they like to make their own patterns as that's were they make money) to meet the specs of the casting process. - JK