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.
Should be the 700R4
it is a 700r4
.035
yes like 350 engine
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 they interchange
Yes, but the exhaust Y pipe from the 305 may not fit the 350.