Siesta

Hi all ,, was after some specs on R600 macks ,,after 237 top speed and cruise ,, and fuel use ,, im retired and want to use an R600 as a base for a motor home ,, Bit like the B series below only bigger Luton and body.. think there is 3 different lengths longest ,, standard chassis about 4mtr from back of cab to end of chassis any info would be great or direction ..