......put 5 gallons new fuel in the tank .
Drained what I could of the old gas from the lines........There may still be some contaminated gas dilluting the new gas you put in.....and the spark plugs are probably crudball too.
but when I put it in gear it struggles when I push the accelerator pedal .in park it seemes to rev ok. The carb is probably dirty and the accelerator pump is shot.
Also the heat block off valve in the exhaust manifold appears to be stuck could this be choking off the engine ? Naw, it's not going to "choke anything off"....it just directs some of the exhaust heat up toward the intake manifold when the engine's cold. Move it around by hand and try to free it up.
My gut tells me it's a transmission problem as I really gotta sneak up on the throttle when it's in gear or it will die but once it starts moving it seems to gain momentum. Naw, I'm thinking cruddy carb......you could kit it.....or not. The car might run better if you left it on fast idle for about 20 minutes. Just make sure the cooling system is topped off with no air pockets. You did change the oil, right?