If I've read your post correctly you've now got problems with your radiator ?
If it's just a rad then you get brand new ones for less than £100 or depending on what the problem is with yours, get it re-cored ?
Depending on age, length of MOT, Tax and mileage, 3.2 Frontys are selling for anywhere between £600 to £1800 at the minute so if you decide to sell it as a non runner your not going to see a great return on it I'm afraid. The LPG kit certainly makes it more appealing to people but it's not going to fetch much more than a standard one I'm afraid.
My advice, if it's just a knackered rad, spend the £100 and get it sorted. Sell it as is and you'll loose a lot more than £100 I'm afraid.