We run a 7x16 dbl axle and fit a 52TT, 52 V Ride, and a sideways 36 WB on it with probably 3ft to spare. We also have a giant heavy duty plastic tote box as a toolbox on the tongue.
For a 48 and 36 you could probably get away with a 12 footer. If you have any plans to expand in the future get a bigger one.
"Always do your best. What you plant now, you will harvest later."