I have a Clarke strong arm 1T crane and at full stretch can only do 250kg, your engine will weigh that alone, the gearbox assembly a lot less perhaps 75kg , I recall lifting it alone 10 or more years ago although not sure if the overdrive was on at time, so you will need a 2T crane to lift both together. Unless you can do it not on full stretch and then 500kg ok
I have had gearbox in and out fairly easily before I bought my crane and alignment was easier as less weight to rock about.
With crane and swapping engines I tried for a day or too to get the 2 mated , then I bought the engine leveller and got them together in 30mins , i tip I read was to extend some long studding on gearbox to help align the two.