First of all it is an EGR valve obtain a new one and put it back where the old one was.
305 horsepower
235 horse is stock on 98 305
Yes, you sure can.
Yes.
it is a 700r4
.035
Should be the 700R4
yes like 350 engine
Yes they interchange
Yes it will fit right in there with no modifying.
If it has a 305 around 15mpg If it has a 350 13-14
Yes, but the exhaust Y pipe from the 305 may not fit the 350.