You just can't buy RH shrouds from a dealer, there is a member on this site that reproduces the RH shroud so thats OK, but expect to pay in excess of $100.00 Dollars.
The fuel tanks for 84/85 Tecates are easy enough to get. When was the last time you saw an 86/87 Tank for sale............?
$800 bucks, I wish you all the best but I think that you will struggle to achieve what you want for $800. You could sit a motor in a frame for that I reckon. Will it run, be reliable and look half decent, not too sure about that?
My toys 85 KXT250A2, 85 ATC250R, 85 Tri-z 250, 06 LT-R450, 04 YFZ450S, 07 125 typhoon x 3, 06 FPV GT.