you may also look into running some LS1 swap headers for an S10, they are 1.5 primarys and 2.5 collectors, not the best setup, but they are tight to the block and should have all kinds of clearance in your 98 fullsize.

Im building an iron 408 for a buddys 96 S10 that is getting swapped in with a T56 and were using these headers, made by sanderson.

Another option may be some mustang LS1 swap headers, kinda pricey but they are pretty tight to the block and should have enough clearance as well.