pipes length
 

Could any one advise me the correct length for 4 into 1 pipes for 300lb automatic sedan? Pipes are 1.7/8-2.0-2.1/8 pipes
388ci sbf
Specs on SBF 4.155 bore 3.585
stroke, yates heads 373/274cfm, 2.150/1.600 valve
278/300 @ 050/ 115 lobe sep 16.1 comp
engine turns 9000rpm and made 825 hp with cast intake and single dominator. Looking to make 860hp.