There are several JD FEL's that will fit a 1020. 37,48,143,145,175 If you utilize an ind hyd control valve be sure it's designed for closed-center hyd's. For optimum hyd operation control valve return oil should be routed to ported hyd filter cover.
If you have a swept back front axle be careful with a loader. Model 37 loaders work best so look for that or a like size aftermarket product.
Seems to me we used a ported filter cover to supply oil to the external valve and the return line was plumbed into the rockshaft cover where there is a pipe plug. We used the same setup on other tractors for the Deere hydraulic reset plows