On my RRC (so Disco 1) I use every extension I have so that I can reach it form underneath, my head touches the back axle. Buuy a quality inpact socket, they cost a little more fomr Halfrauds but are worth the money, they don't bust, split, spread etc.
Alternatively, I bent a 14mm spanner to fit between the bulkhead and the cylinder head the first time I trie it, then rested a lenght of pipe on the open end of the spanner and belted the other end with "persuasion" (My sledgehammer). The spnner jumped about 14 feet but eventually I won.
I didn't notice what engine we are talking about but the V8 won't fit downwards betweent he engine mounts and neither engine fits upwards whilst attached to the 'box. You best hop is to remove all 4 engine mounts (gearbox has 2) and lift the whole lot forewards whilst you cut the errant bolt away.
Replace 2 of the bottom bolts fo rnow unitl you have remove the top bolt or you risk trashing the bellhousing, gearbiox input shaft and clutch/flywheel.
