Motor Questions

[old Rusty C10]

Ok guysd please bear with me cause im not an expert on these things.
I picked up a 1986 C10 today which has a 4.3 v6 motor in it. She smokes like hell and makes noise on takeoff, and it appears to be a noise from the cam or heads. The truck shows 84K on the clock but the title shows 122,000 so ive got to assume its at least 184K on the motor
based on this im thinking why even bother to change the top half of the motor cause once the top is tightened up the bottom half will go
Heres the questions
Will a 305 bolt up to this transmission and properly work?
What kinds of problems will i have relating to the computer and emmissions and what kind of emmissions fabricating will i have to do?
Someone already disconnected the air pump on this thing just to throw that into the equation
and finally if i was to just replace the 4.3 motor with another one is there a vast power diffrence between the 305 and the 4.3?
I like to try and keep thngs simple as possible so what am i in for with all of this?

[CRRoy71]

I have both of these engines.

I have a '92 ext cab with the 4.3, and my Blazer with the 305.

The '92 has 215k on it and still running strong. No smoke, no leaks, nothing. Oil has been changed every 5k miles.

The Blazer has 106k, smokes, leaks like a sift, and does not have any more power than the 4.3.

If your choice is between the 4.3, and the 305, I say go with the 4.3.

If you want a v-8 to put in it, don't go with a 305, go with a 350.

[TROYLV]

i concur, we have a 4.3 in the 92 s10 and that thing can dance around a 305. do the 350 if you do v8.

[swervin ervin]

No computer to worry about either. Didn't come with one, unless it's a Cali truck.

If I had my druthers, it would be a 350. But, if your choice is between a 4.3 or 5.0, I think I would go with the 4.3 too, as far as a daily driver anyway. The 4.3 V6's were some dang good engines, if properly maintained.

[TIMSPEED]

Lest we forget that the motors that powered the famous cyclones and typhoons, were 4.3L? Also, if you think about it, the 4.3L is basically the SAME as a SBC, except it has two cylinders lopped off. (Even check the bore/stroke size!) It depends, since it's a big truck like a C10, I'd say go with a 350...but that's just me

[old Rusty C10]

Ok lets say i can come up with a 350, will that bolt up to the existing automatic transmission and properly work? i know years ago i had an oldsmobile station wagon when i was an owner of private cabs and i threw a 6 cyliner transmission in it as a band aid fix while i had the th350 picked up and rebuilt and for the time i used the 6 cyl tranny ( the th 350 was vacuum advance and the 6 cyl was torque advance) it didnt have any kind of kickdown cause the two systems were incompatible for the kick down or something like that. IF i come up with a 350 motor mounts and all are the same and the only thing id have to change then is the exhaust Y pipe?
and are ya sure that theres no computer? i thought all vehicles after 1981 had emmissions computer in them? lol my truck knowledge is limited here so please dont laugh at my q's
One more stupid question I have a 250 I 6 in a 1976 c10 would i be able to swap that into the 1986 and bolt that up to the transmission?