I am hoping to retain my 1850 subframe, and use jag engine mounts

as they are available as OE, and are excellent (I borrowed the idea from Caterham, and used them in my spitfire) Helpfully, the mounting centres are the same as dolomite. A simple adaptor onto sprint or 1850 engine mounting brackets should be very simple.
Is there anything I need to watch out for? I guess clearances to rack, bonnet etc are all quite tight? My usuiual approach is to chock the engine in place with blocks, use card to design any brackets, make in steel and tack weld those the original engine brackets in situ. Take off and weld properly.