To build a medernized version of the old Z/28 302 you'd be much better off building with a flat top piston'and mill the L98 heads to 56cc to get a 10:1 finished compression ratio. Now it will run on todays premium pump gas. (based on a 0 deck height) . You'd be much better off using a modern mechanical street roller camshaft rather than the old 30-30 cam. Use a street roller with less duration but more valve lift.
Say the Comp Magnum CS280AR-10 280-280 236 236 .550" .550" 110LSA. Comp #12-702-8
The motor will make a lot more torque and power than the 302 of 1969.
Port the L98 heads with the 2.00x1.56 valves. Use a origional GM Z/28 aluminum hi rise intake manifold
(A holley 300-36 or a Edelbrock Performer rpm is a good substitute) and a 750 cfm DP carb.
Use 1-5/8" long tube heaers.
Combine with a 4speed or 5speed trans or a th350 with a 3500stall converter. The old 302 Z/28 liked to rev and loved gears. This modern one will too. Don;t be shy with the gears. 4.10++