[78_youngin]

Ok, so for starters I have done a couple of motor swaps so am comfortable with doing this even at my young age!!! The thing is though this is my first time messing with an older car and I'm not yet to familiar with the motors and trannys and which you can match with which and the difference in years! XD

So I have a 1978 Grand Prix LJ with the 301...and i was wanting to put a 305 into her...I know i will need the 305 motor mounts and what not, but the thing is will the 305 bolt to my tranny that is in the car now or do i have buy a new one?? And also what year of 305 can i use to do this swap??

[joe_padavano]

I don't think the universal bellhousing transmissions were used in 1978, so no the Chevy motor won't bolt to your BOP transmission.

Of course, the bigger question is, why bother? Let me guess. The 301 is dead and you just happen to have a 305. This is a common answer and rarely the best choice. Consider a 350 or 400 Pontiac motor.

[fast68]

yeah you will want a pontiac engine if at all possible

455 or 350 at least

305 is pointless unless youre gonna spend on it to bore it and better heads and well all that is gonna cost same or more than with a 350 anyways

wasting money really


and wont bolt to the poncho trans anyways unless it is 10 bolt universal but yeah im pretty sure this wasnt until 1980 or 81 anyways when gm was really putting chevies into other division cars and doing weird stuff like that for fuel mileage and emissions stuff

the th200 and 250 and 350 and 2004r were the 10 bolt trannies in the 80s

the th400 variants(3L80 and 3L80HD and others), and the 700r4 trannies were not 10 bolt universal bell pattern

good luck though with what you do do

[1badLemans]

I used to have a 79 gp and man I loved that car. Probably would still have it if it didn't get stolen. I happened to have a 305 in mine that was stock and would lite the tires up. I had a 200r4 trans which was also stock. I say go for it unless you have access to a 350 chev or a 400 pontiac. I believe you can mate any of these motors with any of the trannys that were offered in the gp for that year. You should either have a th350 or a 200 like I did just use an adapter plate for your application. Summit and jeggs have them to mate a chev motor to a bop trans and visa versa for about 50 bux. Also try to use or get the 305 parts as these two engines will have nothing in common including the starter. Good thing is they make all kinds of performance parts for g bodys like yours and monte carlos and malibus like nice headers and trans cross members to run true dual exhausts and even rear end set ups etc. Good luck!

[78_youngin]

Thanks for all the info and help!!!! I decided on a 403 with a turbo 350 Tranny

[joe_padavano]

Originally Posted by 78_youngin

Thanks for all the info and help!!!! I decided on a 403 with a turbo 350 Tranny

You do realize that you will need the frame mounts for an Olds motor, right? Note that the mounts for the 77-90 B-body cars are the same as those for the 78-88 G-body cars, so there's a larger pool of donor cars available. Use Anchor P/N 2328 rubber motor mounts (or equivalent) with those frame mounts and the 403 drops right in.