The 400 has long liners but it also has a long rod that takes the strain off the side wall . I have run the 400 in pickups with 550 hp with out any problems . i run a built 400 with a 250 shot and never had wall problems but you do need to use a truck block the early car blocks are bad news . I split right between the lifter bores . I am running a engine about the same as you but my block is bored .060 and the crank is off set ground .030,this gets the piston to the top of the bore . I am running this in a 3200 pound with driver 1986 mustang with headman 1.7/8 x 3 headers,Ported 4v Cleveland heads and a Holley strip dominate and 850 .