Planning first engine build, need help

Planning a first rebuild i guess is a better title. Never done this before, is an $800 budget too low? I can raise it but how much should it be to freshen up an old slant? Dont want cost to exceed value of the car or else id just swap something beefier in, so i guess 1500 is my hard budget, for 2000 i can buy a 318 and transmission or another car
Last 318 I bought I paid $50 for and was given the transmission for free.... It needed $120 rebuild but that was easier than falling out of bed...
So you haven't started it and drove it in months and months. It could need some good gas it could need a valve adjustment it could need a carburetor adjustment I couldn't need a lot of simple things. You said the previous owner threw a lot of cash at it and it has high compression. Have you tried doing a compression check? where's the oil look like? When's the last time you changed it and the filter? When's the last time you changed the air filter? When's the last time you gave it any kind of serious tune-up like new plugs wires rotor and cap?...
I've never seen one of these six cylinders die but I guess anything is possible. One that was rebuilt and a lot of cash thrown at it to quote you... I think you just need to look into it a little bit more ask some questions and get some more feedback... And for goodness sakes post some pictures of the car.. let's see this 10 to 1 compression slant 6 and how well you take care of it... It should be a real shiner with all this 6al business...