You need to make certain which ecu you have as there are different subframes for age. the tank other than paint is same as other incarnations of that age
There is a place in Belgium believe they are called Red Fox who make mono subframes. A lot cheaper than second hand ones from e bay
https://www.redfoximport.eu/onderdelen-parts/frame/rearframe/, they aren’t currently showing a 16M sub frame but have a ‘racing’ subframe you’d need to modify to hold the engine management box. Andy
How much ? With duty and courier admin, a used, early (pre 2001) mono rear subframe from Italy is going to cost the best part of £900 That’s just ridiculous. Andy