The 400 towers mount to the frame about 4inches farther forward than the 390 towers. Also the 400 towers are wider than the 390 towers.

 

Just reading that post, lasthighboy, I just realized mark a. referred to his truck as a highboy, which was never offered with a 400 stock. But are you saying the FE perches are in the other set of holes than the 400 (rearward holes)? Because the other set of holes is for the 300, which would mean the 300 and FE share the same holes on the frame (towards the front). The 300 is a long engine, I don't think the FE v8 is that long.

 

Actually you could have a 351m-400 in a hoghboy. The first half of 77 still highboy & 335 sereis motors. Have had 2 of them.
John

 

Well I guess I can't argue that. I was under the impression that the 34" wide frame, front to back, highboy had only the FE or 300 6 as an option. And that the 351M/400 was optional after the frame change. Nevertheless, the perches being at 34" frame width would be the same, and that the only difference in perches would be between 300 6 and the v8's. Still looking for v8 measurements.

 

i have a 75 f-150 frame i can get measurements off of later. Has FE towers. Also have 400 towers i can mock up and measure. Post back later.

 

That'd be great! Thanks.

EDIT: I went digging in the snow for a couple hours, and I finally found the 400 perches. I have to let my feet thaw out , so I'll measure them tomorrow.

 

the measurements that you were looking for from what i gathered from your drawing I got 10.5 inches on the drivers side and 7 inches on the passenger side. this is with FE towers bolted in place, measuring from the center of the motor mount hole to the ouside of the framerail. I also measured the FE and 335 towers from the center of the motor mount hole to the center of the top framerail bolt hole in the tower and got 8.5 inches for both on the drivers side and about 5.5 on the passengers side.

 

Offset of 1 3/4". The frame rails are centered in the truck and are for the most part, symmetrical. You can measure anywhere, for the most part, from the frame. Do it as close to vertical and horizontal as you can practically get. I used a 48" level, and a plumb bob.

 

and to correct my previous post, the 335 towers mount farther rearward on the frame than the FE towers

 

Thanks! I thought they were the same side to side, just wasn't positive. I updated the diagram (I'll add the fore/aft FE-300 vs. 302-400 distance later)

 

So the next question is the bell surface to motor mount/perch bolt. I got 12" or so on the 351M and ~17" on the 300 (other perch in forward frame holes), so does anyone know the FE measurement? It would seem to me the perches have to be in the rear holes for the FE.